I think that how big those problems get is going to depend on how much critical infrastructure we can hack back into a working state despite the fact that it can't phone home, which is going to be a problem if nobody knows how to work offline anymore.

Or, if it's a political scenario, it may depend on how well we can coordinate en masse without the cut connection. If we can exceed a certain threshold then we'll have removed the incentive to cut it in the first place.

Especially if the problem was due to a lack of electric grid as they're suggesting.

Self-hosting gitlab is not and has never been easy if you do it right, it's very heavy on resources and take lots of time and effort to upgrade. It's also extremely complex and has many moving parts. Stick to gitea or forgejo, they upgrade just by restarting the daemon. MySQL for the database if you want comparable ease of maintenance (same thing: upgrading between major versions requires replacing the binaries and restarting the daemon).

I doubt it, I don't think the distributed stuff is anywhere near ready. Instead it'll be time to kiss the ring of whoever manages to grab control during the gap.