I dont use docker anymore (podman ftw) but that is unfair criticism of docker.

You can use any container registry (including self hosted) with docker and it will work. Last I checked, you cannot use any other repo at all with snap without recompling it to add support for your snap repo.

It's so upsetting that canonical will continually come up with cool tech, try to keep complete control over it and ideally make it so it long term becomes the only option, which people understandably don't jive with. Had they learned that in the space theyre in an open approach works better, we could still be using mir, upstart and most importantly unity now. God I miss unity.