There are actually very few alternatives for the autobuild part. The only alternative that I'm aware of is Quay, others require you to roll out your own build & push process.
It's not that hard to roll your own (I'm doing that). It's not trivial, but if you need autobuild rather than just tags, it's not a huge time investment either. Some systems have all the necessary stuff exposed as plugins too (for example buildkite)
