Since it has come up twice, obsidian is a great notes app. The note files are plain markdown making them portable and editable in any editor, if it were to go away you can't lose your data.
There is a paid plan where they sync inside the app for you. OR, you can use ANY file sync you want to keep your phone and pc in sync. You will know exactly where your files are and they are plain text so no risks of weird binary files getting corrupted or weird file locks.


