I looked at every note taking app out there and finally decided to just write arbitrary text files and sync them with Syncthing. I am using the Kate editor on a Linux for this. (I don't use it for anything else) My requirements was that it had a search interface that can go into directories and that it displays a simple directory/file view. It does both great. On Android I use a similarly capable simple app called Markor which gives me a view into the exact same directory tree. Markor also has a good search.

It would really be hard to convince me to use any proprietary format for notes now.