If you are already using a password manager, why not login using password? No 3rd party dependency and risk, and no need to remember how you signed in.
I'm not responding to the question being asked, I'm responding to the people answering it.
When I used third party login the whole point was that if I saw it was available, I was sure I'd use it, so I didn't need to store or remember anything. If I tried and it didn't work, I knew I didn't have an account.