The only Git GUIs that I've ever liked:
- GitX, and its many forks. Mac only though.
- Git Extensions. Terrible name, but this is actually a standalone Git GUI and is surprisingly decent. I think it started Windows only but maybe there's a Linux port now.
- VSCode's "Git Graph" extension. It's not quite as fully featured but it integrates well into VSCode and is pretty nicely designed.
I've tried almost all the others (SmartGit, Sublime Merge, GitKraken, etc.), and didn't really like how they worked.
Only a Linux user's answer to "how do I install software that's not packaged for my distro" would be "don't".