Check out https://www.giuspen.net/cherrytree/, lightweight note-taking app with interesting scripting function built in.
Even if that’s not your cup of tea, it has the option to save your notebook to a single sqlite file, so I take that as good enough proof it’ll work for your similar purposes as well.
Your initial post and response here describe my position as well.
Simply put, to follow individuals, you have to be where those individuals are. On Lemmy here in looking for topics and discussion, those are much easier to decentralize.