[pascalxus]

But, if you use Google Voice number on your other Gmail account, they say it's not recommended because you can get locked out of both.

I think you can use Google Voice number on everything other than your main Gmail account.

So, to be extra safe, after you've set up your 2FA for gmail, make sure to change your recovery phone # to something other than your main telco or google voice number.

[txmx2000]

Same account. You can use the Google Voice number to 2FA its associated gmail account. A printed backup key will protect you from getting permanently locked out. But nobody will be able to login without physical access to your device or printed key.

This is how 2FA was meant to work. It should always require a physical device only you have access to. Otherwise it's just using 1FA two times.