I found this post Is there a way to use Firebase Legacy console from new account where it states that
It is no longer possible to sign up in the legacy console.
But if I have been added as a collaborator on a project in the legacy console, is there any way I can access that project?firebasefirebase-databasefirebase-console
I don't think there is. The owner of the legacy project can add you via email, but if you don't have a preexisting legacy console account the auth workflow won't work. You'll just end up cycling through google logins and back to the new console.