Did you solve this? I am having the same issue.

No, no solution for it yet. Had a discussion about it with EPiServer support but couldn't get anything to work and the last thing I heard from them was "I've created a support case with our developers and hopefully they can give some input on the subject. I'll update when I have any new information."

If you run this by the EPiServer support you can reference ticket #40374 which was my ticket regarding this.

I have had a long unsatisfying conversation with episerver support (ticket #42064). Not able to get any useful information from them. They just keep referring to http://sveinaandahl.blogspot.se/2015/08/how-to-integrate-aspnet-identity-with.html, where the episerver aspnetidentity is not even used :(

I will try to reference your ticket.

Hey, did you guys manage to resolve this? I'm facing a similar issue while trying use a custom UserManager.

No response from EPiServer support. Yet.

Thanks.

I've managed to get the Episerver application use my custom UserManager (SiteUserManager : ApplicationUserManager<TUser>) by explicitly registering its factory callback for the AppBuilder:

app.CreatePerOwinContext(new Func<IdentityFactoryOptions<SiteUserManager>, IOwinContext, SiteUserManager>(SiteUserManager.Create));

I'm still calling AddCmsAspNetIdentity<SiteUser>() to ensure all the other UI* providers and managers also get created for Episerver to use and then later replace the existing instance of ApplicationUserManager within the context to use SiteUserManager instead.

context.Set<ApplicationUserManager<SiteUser>>(siteUserManager);