I tend to prefer "file centered" apps, there's some cool one you'd use with Syncthing?
My favourite is KeePassDX; I would love a notes app with a 'material you' UI.
Obsidian is not FOSS, I still use it because I find it to be the most complete note taking app. You can download it from the Aurora Store and disable the network permission, same on linux downloading it from Flathub and disable the network permission using Flatseal
I've been using Markor to take notes for a year or so now, and I really enjoy it. I use SyncThing to cloudify my Markor notebook directory, and I edit the same files on my laptop using VS Code.
Haven't tried it, since I only sync with my PC and cloud server. But I just checked up and Librera has an option to save progress and profiles to a custom directory, so I guess that would be the way.
Simple notes has a file based option that may be worth a shot. I also backup my contacts ".vcf" file, my AntennaPod database, and my Feeder RSS feed list with Syncthing.
Ahhh ok. I use Joplin and sync with syncthing. I use the file system storage setting in joplin, and my notes sync across my tablet, phone, desktop, and laptop.
Not an easy step to find a text editor I like. I've tested pretty much all the ones I can find, the most decent UI is probably Orgzly but I had sync issues in the past, and it's just a decent UI.
Not sure if this will help you stick with orgzly, but it synced very well with Nextcloud. Must admit Nextcloud was easy, so didn't need to manually sync it any other way.
Well, since you love KeePassDX as me, I started to use KeePassDX as a "database of notes".
Under Root, you can create categories by adding 'Group's.
Inside each group, you can add an 'Entry' (a note).
each Note, will have a sub Category (Title), subject of note (User name), url and the note itself (note).
you can also add tags to your notes.
Give it a go, you'll be surprised how well this works, finding/searching for whatever is there.