Ubuntu is a fork of unstable Debian packages. You don’t want unstable on your server!

Unstable does not mean crashes all the time. What makes them unstable on Debian is they can change and break API completely. But guess what, Ubuntu freezes the versions for their release and maintains their own security patches, completely mitigating that issue.

There are other reasons you might not want to use Ubuntu on a server but package version stability is not one of them.