https://forums.docker.com/t/non-dockerhub-registry-mirror/126552

perhaps, there is no other way besides retag.

docker pull registry.k8s.io/etcd:v3.6.8
Error response from daemon: failed to resolve reference "registry.k8s.io/etcd:v3.6.8": failed to do request: Head "https://europe-west4-docker.pkg.dev/v2/k8s-artifacts-prod/images/etcd/manifests/v3.6.8": dial tcp 173.194.203.82:443: i/o timeout

ctr image pull registry.k8s.io/etcd:v3.6.8
ctr: failed to resolve image: failed to do request: Head "https://europe-west3-docker.pkg.dev/v2/k8s-artifacts-prod/images/etcd/manifests/v3.6.8": dial tcp 173.194.203.82:443: i/o timeout: context deadline exceeded

ctr images pull --hosts-dir "/etc/containerd/certs.d" registry.k8s.io/etcd:v3.6.8
registry.k8s.io/etcd:v3.6.8                     saved
└──index (397189418d1a)                         complete        |++++++++++++++++++++++++++++++++++++++|
   ├──manifest (3ea799f4e1bb)                   complete        |++++++++++++++++++++++++++++++++++++++|
   │  └──config (62bc5b07b564)                  complete        |++++++++++++++++++++++++++++++++++++++|
   ├──manifest (aa2b41e3f99c)                   complete        |++++++++++++++++++++++++++++++++++++++|
   │  ├──config (ee85eb1f0edd)                  complete        |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (8c02b6f8ac46)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (688513194d7a)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (bfb59b82a9b6)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (efa9d1d5d3a2)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (b6824ed73363)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (7c12895b777b)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (3214acf345c0)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (5664b15f108b)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (27be814a09eb)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (4aa0ea1413d3)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (da7816fa955e)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (9aee425378d2)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (a00667e02fad)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (f097e84ccded)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  ├──layer (c39cffd75ba2)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   │  └──layer (4c78bfe85422)                   extracted       |++++++++++++++++++++++++++++++++++++++|
   ├──manifest (82bf8bc50b9a)                   complete        |++++++++++++++++++++++++++++++++++++++|
   │  └──config (6da6ea097b38)                  complete        |++++++++++++++++++++++++++++++++++++++|
   └──manifest (84414327dd1c)                   complete        |++++++++++++++++++++++++++++++++++++++|
      └──config (49ac3c175d7d)                  complete        |++++++++++++++++++++++++++++++++++++++|
application/vnd.docker.distribution.manifest.list.v2+json sha256:397189418d1a00e500c0605ad18d1baf3b541a1004d768448c367e48071622e5
Completed pull from OCI Registry (registry.k8s.io/etcd:v3.6.8)  elapsed: 18.2s  total:  21.8 M  (1.2 MiB/s)