We have an existing user database that we would like to use as a "Member" provider in Umbraco. We don't even want Members to appear in Umbraco, we want the whole membership system to be outsourced to our existing database. Is this possible? From searching and documentation, I can only find information on "external authentication providers" but they still use the Umbraco membership system and the Umbraco member database. For example, I want to restrict access to pages to a Member group, using Umbraco "restrict public access" functionality, but I want the logic for authorization and authentication to use our existing user database. I don't want to create Members in Umbraco, I want the access check to use our existing user database.

Hey. Have you come across this discussion yet in your research? Suggests someone has had a go at implementing “virtual” members https://github.com/umbraco/Umbraco-CMS/discussions/12741

I had not. Thank you, that looks very interesting!