Maybe get a cheap MVNO SIM like Ting Mobile and use that to register?
I know I've had google accounts that didn't require any re authentication in the way of phone numbers for going on years so you can likely discard the number after you show you are human.
I'm sorry, I haven't registered a new account in a while. I tested an account I've had since 2016 that I made with a ex employer's landline phone and I've never registered a credit card to. It is able to play age restricted video by confirming that I want to and nothing else. It's under a fictional name and birthday etc.
I know I've had google accounts that didn't require any re authentication in the way of phone numbers for going on years so you can likely discard the number after you show you are human.