Well, do you think its relevant to support anything else other than Git nowadays?

Yes. There are people who prefer Mercurial than Git, and there are quite a lot of projects out there which still use Subversion.

I really don't understand the mindset that leads to a belief that a monoculture is good or desirable.

Allura might do a bit more on that (...)

Yes, it does.

(...) but Gitea has way more features and the UI is actually decent.

That's debatable, but to each its own.

Perhaps this could shine some light on the "do you think it's relevant to suport anything else other than ".

Not OP, but personally yes. Every code forge supporting only git just further enforces git's monopoly on the VCS space. Git isn't perfect, nor should be treated as perfect.

The above is probably the reason why so many alternative VCS's have to cludge themselves onto git's file format despite likely being better served with their own.

Interesting new VCS's, all supporting their own native format as well for various reasons:

• pijul
• sapling
• jujutsu

Sapling is developed by meta, jujutsu by an engineer at Google. Pijul is not tied to any company and was developed by an academic iirc. If you're okay with not new:

• mercurial
• fossil
• darcs

VCS's are still being itterated on and tooling being super git centric hurts that.