CNCF has harbor [0], which I use at home and have deployed in a few clusters at work, and it works well as a pull through cache. In /etc/containers/registries.conf it's just another line below any registry you want mirrored.

    [[registry]]
    location = "docker.io"
    [[registry.mirror]]
    location = "core.yourharbor.example.com/hub"

Where hub is the name of the proxy you configured for, in this case, docker.io. It's not quite what you're asking for but it can definitely be transparent to users. I think the bonus is that if you look at a podspec it's obvious where the image originates and you can pull it yourself on your machine, versus if you've mutated the podspec, you have to rely on convention.

[0] https://goharbor.io/

▲ alias_neo 2 days ago | parent | next [-]

I would add, for anyone not familiar with it, that this (and more advanced mirroring, etc) is just as easily done from the really nice Web UI (if that's your cup of tea).

	▲	andrewstuart2 2 days ago \| parent [-]
		Yeah, to clarify, I had to first set up /hub as a caching proxy using the UI. Then the above configuration change was what I needed on my nodes in order to transparently use the proxy without changing podspecs.

▲ esseph 2 days ago | parent | prev [-]

Seconding harbor