"git" is just a command line utility.
"github"/"gitlab"/... are all just build around it.
To install git, you do something like (depends on the version of linux)
But before you do, just open a terminal, and type in "git" and see if it is there already.
Many distros have some sort of GUI "software" installer. That may not offer "git", because it only does GUI, but it may offer "kgit" or "gitgui" (one of the frontends), and then it should install git as dependency).
There are others:
https://git-scm.com/downloads/guis
Again: "git" is a local program. git needs no server. git needs no web-service.
Look at my steps earlier to create a new git repo.
Also check our wiki, it has a few steps.
Mind you, git is extremely powerful. And while you can get the most basic steps
git init
git add
git commit
git log
git checkout // or better: git switch
and then later
git branch
git restore
git stash
git push // git pull
....
You will keep discovering and learning. And you will make error are couple of times, and it can get rough.
1) Don't force git, when you have files that you haven't committed yet. You can make git overwrite them. (And you probably don't want that)
2) If you end up lost, ask other first, then try your own. (or backup the entire folder: .git and all files)
If you had a file committed, (so long as you don't play in the .git folder) then the file can be restored. Even if you can't see it, even if you think you deleted all references. git has an internal recycle bin, that keeps between 2 and 6 weeks of data. So files are there.
Except: if you had never committed them.
But then, the problem of overwriting files existed before git.
The first couple of month, when I wasn't sure, I copied the entire folder (files and .git) before doing something that I hadn't done before.
I know it sounds scary. But it is worth it. Really.
Once you done the basics, you can set up git, to mirror into a 2nd folder. Then even if you delete the .git in one folder, you still have it in the other.