Probably a naive question, but is there some way for all these elements to held in a git repo as well? Just move all your issues/trackers to another platform?

There are some approaches, e.g. https://github.com/dspinellis/git-issue

But I don't think there's much standardization around this type of git usage, and I'm not sure how efficient it would be for large repos.

It can probably be done but some projects have thousands of issues, thousands of PRs with dozens of comments in every thread.

It doesn't seem like a good idea to make your git repo store all that data.

and users. GH, GL, BB are kind of dev social netwoks. Project assets can be archivised/mirrored easily with tools or API scripts, but there is no way to link them back to live users. Community needs to be rebuild at new place and thay is lot of effort.