'2021Q3' does not appear to be a git repository

Hello,

I’d like to MFH some commits, but I cannot get the branch 2021Q3.

Trying `git checkout 2021Q3' gives:
error: pathspec '2021Q3' did not match any file(s) known to git

No more success with `git fetch 2021Q3':
fatal: '2021Q3' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights

I have no problem with the main branch. For info:
$ git remote -v
origin  https://git.freebsd.org/ports.git (fetch)
origin  git@gitrepo.freebsd.org:ports.git (push)

Any idea?
-- 
Th. Thomas.