TION NO: 105Universal Containers wants to allow its customers to log in to its Experience...

If the third-party authentication provider supports only the OAuth protocol and not OpenID Connect,then an identity architect needs to create a custom external authentication provider for it. A custom external authentication provider is a configuration that allows users to log in to Salesforce using an external identity provider that is not predefined by Salesforce. It requires implementing the Auth.AuthProviderPlugin interface and defining the OAuth endpoints and parameters.