I feel like a lot of these features could be handled with git-notes[1]. For example git-appraise[2] uses the git-notes feature for a code review system:
That said, it seems like there was a resurgence - I found two, git-issue [1] and git-dit [2], that have both had activity this year. And git-dit has shown up on here at least once before, as well [3].
[0] https://github.com/aaiyer/bugseverywhere
[1] https://github.com/dspinellis/git-issue
Right now they do still unfortunately come off as toy examples once you get to the point where their distributed nature would normally come in handy. It's a shame that the interest in the problem died down a few years back around the time you noted.
Now I'm wondering if someone has implement a release tracker using git-notes. After you tag the release you could build / generate the output assets (e.g. binaries), upload them to some remotes (e.g. S3, GitHub, your server), and add a note with the release info plus some links.
I've already thought up a couple ideas for things that could be built on top of git-notes.