I too was hit by this a few months ago, after having to create a Google account for work, and worked around it by running an android emulator where I installed their authenticator app. This was enough to get past the stupid "you have to have a phone" requirement, and gave me access to the TOTP secret, which I then promptly added to my favourite open source 2FA utility.
Screw you, Google, you're not getting my phone number.
Screw you, Google, you're not getting my phone number.