I was going to switch to trillium next, but in the end I decided not because it relies on a database even more than Joplin does.

I'm in the process of giving Silver Bullet a try. It seems to be pretty well designed. I don't really like that folders are just cosmetic and not useful for navigation, but I like that it is open source, that the documents are saved in the file system, and that it's self-hosted instead of synced.