MarsSeed [1] filed a deletion request for gtk-sharp-2-git [2]:
Obsolete. Upstream repo is archived since Oct 1, 2024.
Also the used branch, 'gtk-sharp-2-12-branch', has not been maintained
for 3 years. [a]
Arch extra repo still carries the last stable release. [b]
[a]:
https://github.com/mono/gtk-sharp/tree/gtk-sharp-2-12-branch
[b]:
https://archlinux.org/packages/?q=gtk-sharp-2
[1] https://aur.archlinux.org/account/MarsSeed/
[2] https://aur.archlinux.org/pkgbase/gtk-sharp-2-git/
Unfortunately it no longer build
