I didn't enable it because I wanted it for security, but because twitch required it. And then I have set it up with TOTP for security while I was doing it, which does not work anymore either. Also, I did not kill the phone number, it is a public phone number that doesn't receive messages anymore. And if you blame me for not wanting to give up my own phone number, I don't know that to tell you. My privacy matters much more than caring about the possibility that someone finds out my 30 long random password and catches the SMS code from the website where they were shown.

I can see the support not doing much. I'd be pissed if someone could just contact support and deactivate my 2FA method

The 2FA prompt itself tells to contact support in cases like this.
Other than that, email verification is perfectly fine for verifying that it's me. The address was never changed. Actually, as I have seen in a friend's account they are using email already as 2FA for logins, if you don't have any other way set up, maybe for other functions too.