Graphing_Graphene
after 2 weeks they all required a phone number for verification
I have managed to get around this by adding TOTP 2-factor authentication (they say you need Google Authenticator but it works in any other app like Aegis or Bitwarden). The problem is that to be able to add TOTP 2FA, you need to either give them your phone number or connect a device with it.
I had an old iPhone lying around so I downloaded the Gmail app, logged in to Google. Then I set up TOTP 2FA in the account settings (this was now possible as I had connected my iPhone to the Google account). Then I deleted the Gmail app and remove the iPhone from my devices in the Google account settings. I've never been asked for a phone number since (actually - I've been asked lots of times but could always skip).
(The reason I did this with an iPhone and the Gmail app is because this way it doesn't "infect" the whole device. I think if you try it on an Android, it will connect your whole device to Google with all the other services like Play, Calendar and Drive. Maybe a throwaway profile on GrapheneOS could be a good alternative.)