Require SSO for all but a few users

We want to require SSO for our Users, but we have a few accounts that are used by Departments to host Webinars, so they use a shared email address for hosting.

We want to allow those accounts to sign in with email address and password, but all other accounts to require SSO.

I cannot figure out if this is possible and how I would go about setting it up.

I have SSO set up and configured, so that is not an issue.