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.
Can you elaborate on this please - what’s passthrough and dts?
I have a shield - can I use it as a server, or is it just a client?