You can rent a burner SMS number for a couple bucks on a site like https://smsprivacy.org/
Re:We Got Phished
by calvano915 on Monday October 24, 2016 @05:00PM
(#12782854)
You could create a Google Voice account with a free number and link to that. Set it up so calls/sms/etc go nowhere but can be changed if you need to restore your Gmail account later with that number.
How recently have you tried to do so? I tried a couple of months ago to set up a Gmail account with a Google Voice number for verification, and it refused to let me with a message which I recall as being vaguely like "This is not an acceptable verification number".
You cannot skip this step on GMail, or at least I couldn't find how. I know you can use the app afterwards, but not before.
Other sites just give me the code, as you say. But not GMail.