Anything really. Just use Docker/Podman or LXC and then the base OS won't matter.
- Ubuntu is still fine
- Debian I have personally used and it is good
- I used openSUSE Slowroll for a while as well
- Fedora server is just as good as RHEL derivatives IMO
Next thing I am looking at is secureblue for Fedora CoreOS. Security matters and a rock solid base with hardened defaults is really nice. It also is Atomic and because it is effectively just CoreOS, you install it with a JSON file (I think). Using the provided example butane file it took like 30 seconds to install. Now I need to customize it further.