How Sitecore and Umbraco can work together in a composable DXP solution by using the same identity provider
I will demonstrate how you can login to both Sitecore and Umbraco with the same identity provider.
Custom identity provider in Sitecore
Sitecore Identity was introduced in Sitecore 9.1 and uses the new Federated Authentication functionality. By using the same techniques as Sitecore Identity it's possible to implement a custom identity provider with OpenID Connect.