Thanks, yes. I expected that to pop up as an option in "try another way" but the link's a no-op at present or else Firefox is doing one of its silent but paternalistic safeguard routines. I tried w/ Safari too so i dunno.
Well I do have WiFi calling, so I could in fact give Google the mobile number they want, but that doesn't mean I'd necessarily be able to use the phone in that way sometime if the gmail setup went south and I had to try to recover it. I'm moving the one correspondent that matters on that setup to a new account from a different provider I use, and then if it goes south and I can't recover it via a 1F recovery - an email address, then so be it.
(I don't mean to derail this thread from the Google card rumors...)