ASP.NET Core Identity is very good, though I prefer not using the default UI package because a) there's no easy way to disable any of the built-in pages, and b) I customize the UI so much that I might as well maintain my own code.

There are several IServiceCollection extension methods to configure Identity:

• AddDefaultIdentity<TUser>() used by ASP.NET Core Identity UI. It call AddIdentityCore<TUser>() and then AddDefaultTokenProviders().
• AddIdentityCore<TUser>() which is called by AddDefaultIdentity<TUser>().
• AddIdentity<TUser, TRole>() used by IdentityServer4.

I would prefer not to include Role so we don't have to deal with both role-based and claim-based authorization and remember which one is for what. However, AddDefaultIdentity<TUser> is part of Identity UI -- if we don't want Identity UI, we have to use AddIdentity<TUser, TRole>. Other than registering a couple of role related services (i.e. RoleManager and RoleValidator), the rest of it seems reasonable.