2e - First Time Enrollment without using a Phone Number
If you have Chromebooks or an Android phone, users can enable 2FA without a phone number by using a Google prompt from a logged-in device.
Below are the steps
Have the staff member log into a domain Chromebook or an Android device
Using a school (or personal) laptop/desktop - have the staff member follow the steps to set up 2FA (again: not on the Chromebook from step 1 above)
Google 2FA will recognize the CB as an android device and bypass the need for a phone number
Continue going through the 2FA steps and select "Use another backup option" when presented with the phone number prompt
Download the codes
Once completed - you are safe to log out of the Chromebook in step 1. The codes will serve as the 2FA method moving forward for that user.
Note: Not tested - whether Chromebooks need Google Play enabled. All Chromebooks tested for step 1 had Google Play enabled. If you are not getting the results above, consider moving the Chromebook to an OU with Google Play enabled.