Is there a way to use a yubi key for the 2FA, or is that an option for in the future?
Yes, but only with a Yubikey that is NFC enabled.
Download the Yubikey mobile authentication app to your mobile device, tap the Yubikey to your device to authenticate. Then add a new account and scan the Umbrel bar code.
Now you can login to Umbrel using 2FA with your mobile Yubikey app + NFC Yubikey.
Thanks, FN1!