I love firefox but this is one hell of an annoyance I would beat author with a large trump. A hellofablob of dependencies etc. Like it was deliberately build to not self host it (and no I dont want docker).
I really really really hate it for almost 10 years. There was a project rewritting it in go but was abandoned and probably the next thing I will develop will be a replacement .
maybe not deliberately, but i can imagine that it wasn't built with self-hosting in mind, until someone (from inside or outside) pushed for a self-hosting option.
is there a documented API? how much does it really take to sync? if it's browser encrypted it would really be just login, push or pull a blob. how hard can that be?