I also do not particularly enthusiastically recommend any of the self hosted alternatives I've evaluated, by the way. But I'm interested to hear from people who have tried one and successfully incorporated it into their knowledge management / research workflow.
@darius There's always Emacs org-mode, and more specifically org-roam which is a Roam clone in org mode. Its just a bunch of plaintext files, so easily synced using whatever file sync solution you want (SyncThing, NextCloud, etc)
I haven't been using org mode very long myself so I cant say much about it yet, but there's an endless amount of articles about notetaking with org mode (with or without org-roam) out there.