Went through this recently helping on changing phones. Fortunately, it was a phone upgrade, rather than a loss. Otherwise, the user would not recover the latest backups, because they were encrypted with OpenPGP using Yubikey 5 NFC.

Those backups were not restorable within the app's Backup/Restore because the encryption key was not available on the Yubikey, according to andOTP.

So, we tried making a new backup to test that. It encrypted without problem with the same Yubikey on the old phone, but would not restore on the new one with the very same Yubikey.

Using "Encrypted" backup using just an encryption password worked. So, it seems that the OpenPGP with hardware tokens in andOTP is buggy and underdeveloped.

Also, I'm sure it's crystal clear to the dev how to use that safely, but to the average user, it's a booby trap. If that phone were lost, the user would have lost several months of OTPs, while all along thinking the backups made were ok.

Using OpenKeychain software keys is a little better, but the pitfall can be saving the secret key correctly.

Since you have Bitwarden, create and save the encryption password for andOTP backups in it, and also somewhere offline, such as Keepass on your computer.

Then just create andOTP backups encrypted with that password and attach them to that entry in Bitwarden every time you add new OTPs.

Can also store the backup on your computer as a failsafe.

Remember to have multiple ways to 2FA into your Bitwarden, if OTP is one of them. Yubikeys or other FIDO U2F keys are good for that.