

Firefox relies on gtk for for those integrated buttons. It’s maybe worth checking that your gtk theme is set to breeze in System Settings > Colours and themes > Application style > GNOME/GTK Application Style (top right …), and that firefox is set to use the system theme.
Those 3 are all fairly similar. Here are some others I can think of:
If you’re not using any of the additional features, cgit should be enough. If you’re planning on collaborating with others, probably Forgejo would be better.
You can also use individual components of sourcehut, if you want a git web interface with just issue tracking, ci, or wiki, for example.