Authy supports TOTP, but also has its own proprietary TOTP-esque format that a bunch of sites & companies use (Twitch and my bank, among them) that can't be copied into another site.
(Yes, it's bad, no, it shouldn't exist, no, I don't know why they don't just <...>, etc.)
(Yes, it's bad, no, it shouldn't exist, no, I don't know why they don't just <...>, etc.)