ok, looks like it is working now, i did:

<https://github.com/rancher-sandbox/rancher-desktop/discussions/1477>

then

vim ~/.docker/config.json

( not sure if this step is needed )

{
  "auths": {
    "priv-registry:5000": {}
  },
  "credsStore": "osxkeychain"
}

FYI there's a #rancher-desktop channel