This is a reason I don’t provide sign up with 3rd party sites like Google or Facebook. The issue is not a Bubble issue, but an issue with any site that uses this signup approach and users who forget how they signed up.

One thing to do, which is extra work, and in my opinion, not worth the trouble of allowing sign up with Google (unless you need their profile details from Google) is to setup the alerts to the user that indicate when they attempt to login or sign up again with the same email address used from google account. In those alerts you can provide the user with the suggestion that ‘perhaps you signed up with google account’…so basically, you do not need to track the method of signup (I believe bubble exposes some values if they signup with google - so they basically track it for you) but when a user is trying to login, you don’t know who that user is, until they enter their email address and attempt to login, so the real work comes at that stage to indicate they already have an account and may have used Google to create it, but that also leads to privacy concerns, since somebody else may be using their email address to check if they have an account or not, which is why Bubble changed the language they use to indicate ‘we did not find those credentials’ instead of the old wording of ‘that email address is already in use’.

Again, in my opinion, more of a hassle than it is worth to give the feature, plus most adults should have a password manager these days, making the need to signup with social media accounts obsolete, as for most users, the benefit was not needing to remember multiple passwords.