Joplin syncs with Nextcloud - Orgzly does too. Agreed, Jtxboard does - via davx5.

I’m currently using obsidian synced via syncthing. I know it’s not Nextcloud, but it works well and has a nice interface and lots of plug-ins - even on Android. It might be able to sync - not bothered trying to yet - if anyone has, please comment.

Good luck with your search.