Additionally, if you signed up with an email and password, you can often just sign in via SSO with a matching email address for convenience and still have the underlying password remain working. Again, possibly not an intentional feature (but rather something like using the email reported via SSO or via email verification as a primary key).
You hope you can ... I didn't login to a Google Account for a few months now and it suddenly wants a lot of personal details to do additional "verification" because I am "suspicious".
Then go through each service and email them to have them try and move your account to new accounts with a traditional username/password login. Some might even be able to change your login method to username/password without requiring a new account!
Alas, short term convenience can lead to long term troubles.