I do agree that adding some kind of backup option is probably a good idea. For many people, losing their email account would mean being locked out of basically all their online accounts (or, in case the account gets compromised, it would mean that all other online accounts would now be compromised too). The majority of people do not use password managers or 2FA, and I’ve made the experience that many people simply cannot be convinced to make online security a priority.
While I’m also a FOSS and online privacy advocate and use tons of self hosted services for that reason, having some way to regain access to their Google account is almost certainly worth the extra data point that Google gets access to. Especially since the likelihood of them already knowing about your phone number is basically 100% if you are logged in on an Android device.
As others have already mentioned, there will be EU regulation that comes into effect soon that will force messengers to be interoperable. Despite following the topic quite actively, it still seems to be quite uncertain how this interoperability will look like. I also have some concerns about companies making interoperability opt-in, requiring users to go to the app settings and manually turning it on or presenting them with a popup that makes it seem like interoperability is a security risk (a Meta spokesperson revealed that they were pushing for a solution like that pretty heavily).
Either way, before trying to get other people to migrate to another platform I would first wait and see what the implications of this regulation are.
I do agree that adding some kind of backup option is probably a good idea. For many people, losing their email account would mean being locked out of basically all their online accounts (or, in case the account gets compromised, it would mean that all other online accounts would now be compromised too). The majority of people do not use password managers or 2FA, and I’ve made the experience that many people simply cannot be convinced to make online security a priority. While I’m also a FOSS and online privacy advocate and use tons of self hosted services for that reason, having some way to regain access to their Google account is almost certainly worth the extra data point that Google gets access to. Especially since the likelihood of them already knowing about your phone number is basically 100% if you are logged in on an Android device.