This is not "encrypted notes", it's "protected notes", it is some kind of access control. I did agree previously (see my post) that it would be a good idea to implement - I presume its API is pretty straightforward to use and just ask for the normal phone credentials (many, many apps do it, the phone is unlocked but asks for pin or fingerprint to go into onenote or the banking app or whatever). Also is much easier to support as you don't need to care about how to recover it if the user forgets the password or something like that, everything is implemented in phone's OS and if they can't unlock the phone they already have bigger problems...

It's even worse nowadays, for the device (not the SD card) I don't think there are still mainstream devices where you can disable the encryption. And even more if you even can root it at all the procedure involves first unlocking the bootloader (again if possible at all, it probably isn't for the vast majority of devices) and this comes with a full wipe of the device. Sure, after you could install your own OS and do anything (including presumably something without encryption at all) but there is not way to decrypt what is already there.