EDIT: You know, after some time to cool off, Google Authenticator 2FA can still be enabled and isn't being phased out like the less secure SMS 2FA, so it's really not the end of the world here. The chance of permanent lockout is avoided, even if the whole Google Prompt system is still wack.
I don't get this. Is this an SMS-based 2FA? If so, I'm not sure that Google has any ability to block that. Your carrier might, though, but that wouldn't be controlled by your device's OS. The option being greyed out on a third-party site has little to do with anything happening locally on your device.
If this is a push-based 2FA, then... yeah, you wiped the device, along with any tokens previously stored on it. This is also why any time you set up 2FA on any service, almost all of them warn you like a million times "If you lose or transfer your device before disabling 2FA, you will lose access to your account" before you complete the process.
This is different. This is something new google is rolling out. This isn't SMS and it isn't TOTP. Google is opting people into push based authentication based solely on them having an android phone associated with their account whether they're still using that phone or not. Anyone not already using TOTP or WebAuthN should really add those to their accounts before Google decides to "help" you by opting you into their new proprietary 2FA.
The problem is they are turning OFF the SMS and instead sending a special dialogue to a nonexistent device for the user to hit a prompt. The device was never used, though, and it was never set up for 2FA. My default has always been SMS which they are now disabling.
Deprecating SMS authentication is a good thing, in all honesty. SMS is not a secure form of data transfer, and is trivially intercepted. You can buy and setup an illegal Stingray device relatively easily, and capture basically all wireless data from a phone within range.
That said, if the device was truly never used for 2FA, then there wouldn't be any push-based 2FA on the account to begin with. Unless there's another device that's been authenticated with your account somewhere, like an old phone. In which case, that's where your login requests are being pushed to. That's a setting that can only be enabled by successfully authenticating with a device at least once in the past.
If there was never any other authenticated device, then that setting on your account isn't there. Enabling that feature is a two-step process, and step 1 involves configuration on a local device before it can be enabled remotely on your account.
If you login to the Gmail app on any device, it can also act as 2FA. Does not need to be the one where they send the push…any logged in device will work.
Microsoft then forcing you to authenticate using the device that is only tied to your account via purchase, and NOT login records, AND disabling other forms of auth
If installing linux was a feature sold to you by Microsoft, and then Microsoft removed the ability for the feature to work on Linux, then that would be accurate.
Cool but that doesn't fix the fact that the default method is one that literally does not function and can result in a permanent lockout. Though, I admit, SMS is way less secure than the Authenticator App.
It's the default because you made it the default. Change your damn security settings Google can't do that for you! Quick to rant about something without knowing how it works or how you got there is on you and not Google.
Even if you turned it back at this point, it still wouldn’t work.
This is pretty infuriating though; Google works just fine with any device that doesn’t run Android so why would they care that you’re running a custom ROM?
My guess is something less evil and more mundane: something about your number changed in their system and now they can’t send codes to it, which is why it’s grayed out. Maybe it was previously classified as a mobile number but now is classified as a landline.
Your only option, if you don’t have any backup codes, is to use that “Get Help” option they have that takes a few days and then either start carrying around backup codes, a Yubikey, or De-Google.
As a few people pointed out, it's only SMS thats being phased out, so using Google Auth is a superior option if you still have access to set it up. But yeah, backup codes would be great for those already locked out by accident.
Using your device to do whatever is op's right. From reading the post, it seems to me that the problem is that they disable other forms of auth. This is for sure intentional, or at least a low priority bug for obvious reasons. I had the same issue, but it was failing to pull up the menu in my stock nothing phone 1. It got fixed later, but why are my backup emails or phone numbers not being used as other forms of 2fa. That is when I realised that despite my efforts, I have ended up relying on Google too much. In the process of changing that, even if it costs me money to host the servers.