The one I ran into recently was Discord. I use Skype to front all of my SMS. Unfortunately, the SMS-in numbers are not tagged "mobile", so Discord refuses to accept them. Their "solution" is for me to register another account and hope I do not need to provide my phone number... Despite my specifically pointing out that the only reason I need to do this is that Discord allows their servers to require this kind of verification.

Ah well, guess I cannot be a Discord user.