I believe I discovered a bug in the app: if you long press a secret > edit > leave an empty string as the comment, and then export a QR code containing this secret, your other device will fail to import ("QR code cannot be interpreted.").
I've only seen this happen with secrets where the comment is put in parentheses and appended to the regular, immutable name of the secret. There's another type of secret where the entire name can be edited, this I did not test. But if you try the import/export flow on a secret whose name contains `()` I bet you'll hit the bug.
I briefly tried Aegis but you must have Aegis+Authenticatior installed, and be root, or you can exfiltrate Authenticator's database file from private storage, which best as I can tell, also requires root. Shouldn't have gone with Authenticator at all, I've learned.
It seems optimal to simply retain the original secret (QR code or whichever medium) you are given when 2FA is initially enabled.
Later found this equivalent: https://mattscodecave.com/posts/how-to-move-from-google-auth...