Can't login on new iPad

That’s encouraging.

I have two suggestions, based on older threads:

  1. Set up an alternative 2FA method, log in to the iOS app on your iPad using the alternative 2FA method, and subsequently try to log in again on the iOS app on your iPad using the Yubikey (source).

  2. Instead of a USB-A to Lightning adapter, try this USB-A to USB-C adapter, or perhaps something equivalent (source).