I’ve recently been looking into mysudo. For $1 a month you can get 1 number as well as some extra stuff if you care about that.
You can use it without Google services if running GrapheneOS but it takes a second normal phone and a throwaway Google account to work. Incoming notifications don’t work but if used as a spam number that’s probably a good thing lol. (https://support.mysudo.com/hc/en-us/community/posts/4414403558555-When-will-MySudo-be-supported-on-GrapheneOS-?page=1#community_comment_4414489480859)
Haven’t pulled the trigger on it but seems like something I will probably set up at some point
SMS is unencrypted, insecure, and not private to begin with. Your SIM provider can see everything you send plus track you via cell towers.
As someone who is currently de-googling my own stuff I understand but wanting google services but please don’t think it being Google is why it’s not Privacy focused.
Then a Google voice number is fine for that. Just create a junk Gmail and had that number out.