Does anyone know if there's a decent, comprehensive library that handles all authentication / login for .Net Core apps? Bonus points if there's a SSO addition (even if that part is commercial).
Identity.NET for embedding a library, Identity Server for hosting a service.
They're not the simplest, and unfortunately the scaffolding story with Identity.NET is a bit of a nightmare for MVC apps (if you're not careful, you can end up with a ton of hidden-but-accessible razor page endpoints), but the code is robust and most cases are covered.
Identity.NET will also need you to write your own implementations of a couple of database access classes if you don't want to drag a dependency on Entity Framework Core along for the ride.
Documentation is fairly dry and mostly complete (Microsoft style) but be careful with versioning because dotnet core moves fast.
