[dmm]

> the idea of having to go fetch my backup key out of a safe to register it (and hope the site allows multiple keys) just feels impractical

An alternative some people use is to register a TOTP code and print out the QR code. Then you can remove it from the app. It's not a full solution but it might be part of one that works for you.

> Wish there were a way around this :/

Sign in with Google/Facebook/Github. I wish sites supported custom OIDC but that's probably impractical.