IIRC, Twitter, Google, Dropbox and Facebook also don't allow to enroll multiple Yubikeys (ETA: Looks like I'm a bit outdated).
In general, most platforms don't really account for the scenario "my 2nd factor got stolen/robbed/destroyed/lost" beyond also offering a phone app and printed recovery records - and the end result is that a house fire, flood or storm scenario locks out users permanently.
In general, most platforms don't really account for the scenario "my 2nd factor got stolen/robbed/destroyed/lost" beyond also offering a phone app and printed recovery records - and the end result is that a house fire, flood or storm scenario locks out users permanently.