I am in the process of hacking a vending machine, I have reported the details of all my findings to the company but i wanted to dig deeper.

The vending machine has a screen which runs android with an application pinned to the screen on which users can buy stuff. i found a way to bypass this application and slowly found ways to interact and get access to almost everything in the complete device.

I can install software on the device and wanted to install a keylogger, the one i tried does not log passwords so i wanted to know if there are any keylogger applications or related services which can log all the keys, be it in a password field or any different field ?

I also wanted to explore any other vulnerabilities i can find potentially, if you have any resources or how can i build some related skills to such hacks, please link.