I see monodevelop isn’t active since 2019, maybe our mono6 is too recent and not correctly recognized 
this is the mono version you get with mono package.
what about nix-shell -p mono4 ?
I see monodevelop isn’t active since 2019, maybe our mono6 is too recent and not correctly recognized this is the mono version you get with mono package.
what about nix-shell -p mono4 ?