I've used a google voice number as my primary number for quite a while, and it's actually pretty rare to have issues with it. I'd say that much less than 1/10 of services require me to use my cell's actual number.
Google
Voice needs to be linked to a valid +1 land or mobile number to function long term. My google voice number lasted for almost exactly 6 months after the us cell number it was linked to was disconnected (moved overseas for a while). It’s classification as a valid mobile lasted a bit less long and now I can not use it to send/receive SMS at all (voice mail works but it will not ring through and I can no longer use it to call. Before that many banks etc stopped
Sending SMS 2fa messages through (as the are supposed according to latest NIST guidelines). Thankfully (?) the same banks seem ok to do voice 2fa to my overseas number. Sadly the still do not support better mfa Authenticators.
Would love to know how to maintain a US SMS presence without sketchy obviously for spammers products.
I've been using jmp.chat and have been pretty happy with them. But I haven't tried using them as 2fa provider, they may be blocked by places that block common voip providers.