Debian/Ubuntu packages doesn't have 10/11

LLVM Project
1

At the moment there aren’t packages up for llvm 10/11 despite https://apt.llvm.org/ saying there are. There also aren’t releases for these version at http://releases.llvm.org/download.html. There are releases for version 10 up on the github.

Is this intentional?

2

Depends on the version of the distro (Ubuntu xenial should have it for example).
apt.llvm.org supports the last three versions of llvm (currently: 12, 13 & 14).

I leave 10 or 11 for the distro supported when they were published.

I hope it is clear!