It's worth noting that a CLEC (or other provider) can, in fact, denote a non-mobile number (or block of numbers) as "mobile" so that it can do things like receive text verifications from short codes (like your bank, or gmail, uses).

This is expensive and time-consuming, however, and almost no CLEC (or other such provider) will do it - you have to petition and register your number(s) with every single mobile provider and get them to accept that these are not sources of spam, etc.

I have this problem because my main, personal number is actually a twilio number (as I built my own personal telco within twilio) and this means I cannot receive validation messages from shortcodes (like a bank). I spoke to some twilio engineers at Signal and they confirmed that it would indeed be possible to register twilio numbers as "mobile" but too expensive ...