Yes, you can use just phone in UNA without email, but you need to wait for the next update 9.0.0-RC10, since it will be possible to login with phone number starting from  9.0.0-RC10, before 9.0.0-RC10 it possible to login with email or account ID only.

Also you will need to open Twilio account and enter Twilio settings in Studio > Settings > Twilio to be able to send verification SMS then change the following option Studio > Settings > Account > Account is confirmed when = phone is confirmed.