Yeah, there's about to be a lot of people heading north. Free movement between states is going to be fought over in the supreme court, because northern states will try to prevent being overrun. Michigan might try to build a wall across its southern border.
I don't have much hope in the future.
I'm mostly convinced that people are going to do absolutely nothing.
Can we pick up Ann Arbor and move it 1,000km north or so?
With github, gitlab, etc etc, you get much more than just a bare git repo store.
My suggestion is to look at the features of each hosting solution and present those features to the team, discuss the pros and cons, and let people decide what they feel is best for the team.
Remember, you're not proposing a simple version control system. You're picking one very important part of an internal development platform: issue tracking, version control, code quality, security scans, developer workflow helper apps, documentation/wiki, build systems, etc etc. Depending on what you already have in the roles other than version control may inform your decision on where to host your git repo.
They gotta bandage their hands then dip the bandages in glue then in broken glass.