[bscphil]

It doesn't support these at my institution. Maybe they haven't rolled out this version? (Technically you can get U2F to work, but they have a bright red warning that says it's unsupported when you do that.)

[w8rbt]

IT admins at your org can enable or disable 2FA methods allowed via the Duo administration console. Many US edus disable TOTP.

[dogma1138]

I think because they don’t want to deal with supporting the app and (almost) everyone has a phone that can receive calls.