The good news is that every self-hoster will be more than happy to start using this hypothetical self-sovereign solution with their data, if and when it becomes available.

I know I would. I'm just not smart enough, nor have the correct kind of experience to start designing, building or evangelizing such solution, so I am stuck waiting for someone else.

A good example is ForgeFed, which I can't wait to mature enough to be usable.