That's not fully correct.
I used the standard version provide with Debian Bullseye initially,
git version 2.30.2
That is giving the issues.
Searching through various forums, I found a hint point to a GnuTLS and that might can be circumvented by a fresh compile version of git which results in
git version 2.37.1
It does not change anything at all. And I reverted back to the standard version anyway.