Need to finish setting up Graphene OS

Use case: A phone to sign up for and receive those SMS texts to verify with, when establishing a new user account. (It seems like almost every account setup is asking for a phone number, then sends a code to that phone.) I have followed the many configuration recommendations on the Pixel 9a / Graphene OS and am now ready to get a phone number. I think I understand that I can do with by using wifi only (and not a cellular service). This leads me to needing to purchase a phone number service that will also allow those SMS texts to be sent to the phone. I can’t figure out if that is an eSim or it sounds like there is a better alternative? Appreciate guidance. It is the last step I think.