git on Debian 10 backports throws fatal: unable to access 'https://github.com/user/repo.git': Failed sending HTTP2 data
Solution 1:
In other computer with the same system, but with git working normally, I compared the packages not upgraded.
Downgrade libcurl3-gnutls to 7.64.0-4+deb10u2 and the problem is solved.
Solution 2:
I also had this problem on devuan. Just purge git and install it from sources. Prefer the last version https://www.digitalocean.com/community/tutorials/how-to-install-git-from-source-on-ubuntu-20-04-quickstart https://mirrors.edge.kernel.org/pub/software/scm/git/
Unpack it, say, in /tmp cd into the unpacked folder ./configure && make && sudo make install
then, which git