@Sven & @unman thanks for your advises and help
I have choosen to install it in my sys-vpn template, being with a fedora 34 minimal template.
In my template I activated the repo for gnubiff like that
dnf copr enable scx/gnubiff
then I manually downloaded gamin rpm in order to get libfam to be able to install gnubiff, here
https://koji.fedoraproject.org/koji/buildinfo?buildID=1677060
and finally
dnf install gnubiff