Just for those people for whom this might be a new concept: There is actually a fair number of these distributed bug trackers: <https://news.ycombinator.com/item?id=22833037>
I looked into them. Most of them use some CRDT-ish machinery to merge concurrent ticket changes. (Fixing merge conflicts in tickets would be too disappointing.) As a CRDT person, I noticed that implementing CRDT merges in git itself mostly makes that machinery unnecessary. Then you can keep your tickets in plain Markdown, having CRDT merges for both code and metadata. I have it working here btw
It may be that the presence of Fossil as a mature option is enough to dissuade people from choosing/working on alternatives. I’m pleased to see git-bug slowly making progress though, maybe it will get there in time.