I seldom join anything these days, but I made an exception & did it today.
They demanded SMS verification even after I used a google sign up.
So...I used our GV number - and it bitched that it was VOIP & refused.
No way was I giving out my Twigby number - but I remembered that some other time my Textnow number had worked, so I tried it - and it did work.
My TN uses are via an unactivated phone via wifi & after it had proven its worth I signed up for their $5/year number holding deal as well as getting their SIM for free cellular.
IMO, since so much is now VOIP, these sites which gripe about it are just stupid - and when the free combo of GV + Obi box may end, we'll just port over to VOIP.MS - which I'm certain will be no different for such SMSs.
'Tis a silly world that we live in !!
PS:
This has come up here before...and has been explained=>