Nitrokey 3 has recently added support for OpenPGP and it would be great if it could be used on Android, for example with OpenKeychain. Although its maintenance is on hold, I don’t know of any other alternatives at this time.
It looks like I was wrong, I tested it today by first adding the public key to the app from a file (since it didn’t want to read it from the token). The application works with Nitrokey 3, successfully encrypts and decrypts files.
It doesn’t work over USB, but it works with NFC. Although on the latest firmware it doesn’t connect, it says that I removed the token too early, although this is not the case. At the same time, a red light is on on the token.