[disadvantage]

> (Authy et al)

I once had an Authy account and then my phone got lost, along with the SIM, and then I had to contact support to change the number attached to my Authy account! I never want to do that again.

I since ditched Authy and now backup TOTP challenge response QR code seed images with KeepassXC alongside any relevant recovery codes. Then I backup the KeepassXC DB locally and in cloud storage. If my authenticator app gets lost/deleted I can re-spawn the TOTP response in a fresh install of the app (importing TOTP).