If you have ssh access to a box; you have a git remote.
It’s obscenely simple, and contra to your claim the “managed” aspect is not the selling point of this software. The selling point is the project management features and integrations.
In githubs case it’s a managed service.
In gitlabs case, I can be a managed service or it can be a software suite you maintain yourself.
Not a universal truth.
I worked at a company that started out with a setup like this for the dev team. It felt like a massive burden was lifted when we moved to Github Enterprise. We weren’t using the project management features at all, just the source code hosting stuff.
Oh wait, git over ssh doesn't show a web view.
Also way easier to send someone a web link to something in a discussion to have them look into it, especially if it's in a different branch then they may have.
What's wrong with fetching it, checking it out in a local branch, and browsing it using your editor? It probably is much easier to browse the code, see it in context and see the diff using your editor compared to the web interface.
There's a bit more to it ... and sure all can be done manually.