[aasasd]

In issues for Orgzly, support for org-crypt was mentioned as a wanted feature, so I guess that's what some people use. However, it sounds like it encrypts text inside files, maybe on per-note basis.

On desktop, encrypting files is usually easier done in separate software, like Veracrypt or the multiple Linux filesystems. However, it's rather slim pickings for that on phones—Cryptomator is one that does that (iirc), but it's actually not open-source for phones.