After some debugging and help from ChatGPT I got the USB HUB working on NuttX. It was failing because the USB HUB driver on NuttX was missing the USB HUB Class 9 with Protocol 2 (Mult. TT HS HUB).

After fixing it everything worked as a charm:

nx_start: Entry
uart_register: Registering /dev/console
uart_register: Registering /dev/ttyS0
work_start_highpri: Starting high-priority kernel worker thread(s)
work_start_lowpri: Starting low-priority kernel worker thread(s)
nx_start_application: Starting init thread
up_release_pending: From TCB=0x20201208
usbhost_registerclass: Registering class:0x202000f8 nids:3
usbhost_registerclass: Registering class:0x20200108 nids:1
imxrt_usbhost_vbusdrive: RHPort1: enable=1
usbmonitor_start: Started: 5
ehci_waiter: ehci_waiter:  Running
ehci_waiter: connected
usbmonitor_daemon: Running: 5                                                     
nx_start: CPU0: Beginning Idle Loop                                               
                                                                                  
NuttShell (NSH) NuttX-10.3.0                                                      
nsh> usbhost_enumerate: maxpacksetsize: 64                                        
usbhost_devdesc: class:9 subclass:0000 protocol:0002 vid:1060 pid:9495            
usbhost_enumerate: sizeof config data: 41                                         
usbhost_findclass: Looking for class:9 subclass:0 protocol:2 vid:0424 pid:2517    
usbhost_findclass: Checking class:0x20200108 nids:1                               
usbhost_idmatch: Compare to class:8 subclass:6 protocol:80 vid:0000 pid:0000      
usbhost_idmatch: To DEVICE class:9 subclass:0 protocol:2 vid:0424 pid:2517        
usbhost_findclass: Checking class:0x202000f8 nids:3                               
usbhost_idmatch: Compare to class:9 subclass:0 protocol:0 vid:0000 pid:0000       
usbhost_idmatch: To DEVICE class:9 subclass:0 protocol:2 vid:0424 pid:2517        
usbhost_idmatch: Compare to class:9 subclass:0 protocol:1 vid:0000 pid:0000       
usbhost_idmatch: To DEVICE class:9 subclass:0 protocol:2 vid:0424 pid:2517        
usbhost_idmatch: Compare to class:9 subclass:0 protocol:2 vid:0000 pid:0000       
usbhost_idmatch: To DEVICE class:9 subclass:0 protocol:2 vid:0424 pid:2517        
usbhost_findclass:                                                                
                                                                                  
                                                                                  
 Class Found!!! 0x9                                                               
                                                                                  
                                                                                  
usbhost_classbind: usbhost_findclass: 0x202000f8                                  
usbhost_classbind: CLASS_CREATE: 0x20208f70                                       
usbhost_cfgdesc: Interface descriptor                                             
usbhost_cfgdesc: Endpoint descriptor                                              
usbhost_cfgdesc: Interrupt IN EP:usbhost_cfgdesc:  addr=1 interval=12 mxpacketsiz1
usbhost_cfgdesc: Endpoint allocated                                               
usbhost_hubdesc: Read hub descriptor                                              
usbhost_hubdesc: Hub Descriptor:                                                  
usbhost_hubdesc:   bDescLength:         9                                         
usbhost_hubdesc:   bDescriptorType:     0x29                                      
usbhost_hubdesc:   bNbrPorts:           7                                         
usbhost_hubdesc:   wHubCharacteristics: 0x0089                                    
usbhost_hubdesc:     lpsm:              1                                         
usbhost_hubdesc:     compounddev:       FALSE                                     
usbhost_hubdesc:     ocmode:            1                                         
usbhost_hubdesc:     indicator:         TRUE                                      
usbhost_hubdesc:   bPwrOn2PwrGood:      50                                        
usbhost_hubdesc:     pwrondelay:        100                                       
usbhost_hubdesc:   bHubContrCurrent:    1                                         
usbhost_hubdesc:   DeviceRemovable:     0                                         
usbhost_hubdesc:   PortPwrCtrlMask:     255                                       
usbhost_classbind: Returning: 0                                                   
EHCI Initializing EHCI Stack                                                      
EHCI HCIVERSION 1.00                                                              
EHCI nports=1, HCSPARAMS=0011                                                     
EHCI HCCPARAMS=000006                                                             
EHCI Interrupt: 000004                                                            
EHCI PORTSC1: 0803                                                                
EHCI Connect Status Change: 000803                                                
EHCI RHPort1 connected, pscwait: 0                                                
EHCI USB EHCI Initialized                                                         
EHCI RHPort1 connected: 1                                                         
EHCI Interrupt: 000004                                                            
EHCI PORTSC1: 0205                                                                
EHCI Hub port 0: Enumerate the device                                             
EHCI CTRLIN/OUT: RHPort1 req: 06                                                  
EHCI Async transfer EP0 buflen=18                                                 
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8c00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 05                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 06                                                  
EHCI Async transfer EP0 buflen=9                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8c00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 06                                                  
EHCI Async transfer EP0 buflen=41                                                 
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8c00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 09                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI EPALLOC: EP1 TYPE=3                                                          
EHCI CTRLIN/OUT: RHPort1 req: 06                                                  
EHCI Async transfer EP0 buflen=9                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8c00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 03                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 03                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 03                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 03                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 03                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 03                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI CTRLIN/OUT: RHPort1 req: 03                                                  
EHCI Async transfer EP0 buflen=0                                                  
EHCI Interrupt: 000001                                                            
EHCI USB Interrupt (USBINT) Interrupt: 000001                                     
EHCI IOC EP0 TOKEN=8d00                                                           
EHCI Intr Transfer EP1 buflen=1


This is the patch (that I will submit to mainline)

$ git diff drivers/usbhost/usbhost_hub.c 
diff --git a/drivers/usbhost/usbhost_hub.c b/drivers/usbhost/usbhost_hub.c
index ee642fbeff..5f0bcf99c5 100644
--- a/drivers/usbhost/usbhost_hub.c
+++ b/drivers/usbhost/usbhost_hub.c
@@ -103,6 +103,10 @@
 
 #define PORT_INDX(x) ((x) - 1)
 
+/* Array size to avoid mistake adding new item to g_id */
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
@@ -184,7 +188,7 @@ static int usbhost_disconnected(FAR struct usbhost_class_s *hubclass);
  * used to associate the USB host hub class to a connected USB hub.
  */
 
-static const struct usbhost_id_s g_id[2] =
+static const struct usbhost_id_s g_id[] =
 {
   {
       USB_CLASS_HUB,  /* base         */
@@ -196,7 +200,14 @@ static const struct usbhost_id_s g_id[2] =
   {
       USB_CLASS_HUB,  /* base         */
       0,              /* subclass     */
-      1,              /* proto HS hub */
+      1,              /* proto Single TT HS hub */
+      0,              /* vid          */
+      0               /* pid          */
+  },
+  {
+      USB_CLASS_HUB,  /* base         */
+      0,              /* subclass     */
+      2,              /* proto Multiple TT HS hub */
       0,              /* vid          */
       0               /* pid          */
   }
@@ -208,7 +219,7 @@ static struct usbhost_registry_s g_hub =
 {
   NULL,                   /* flink    */
   usbhost_create,         /* create   */
-  2,                      /* nids     */
+  ARRAY_SIZE(g_id),       /* nids     */
   g_id                    /* id[]     */
 };