SMS and (at least for craigslist) voice 2FA doesn't work with VoIP (Google Voice numbers, including numbers ported from mobile operators). IRS 2FA via SMS definitely doesn't work, nor does Dunkin Donuts (which invalidates use of their entire app on all mobile platforms). Some services offer voice 2FA which will go through, and some offer email, but many don't. Of course the vast majority of 2FA over SMS work with the major VoIP providers, but if you hit one where it doesn't...there's either no way around it or you have to wait for a snailmail 2FA token (IRS).