You can call "services.AddMenuBuilder();" and all Methods of any Controller in your project which are decorated with the "MenuBuilderAttribute" get collected to a MenuBuilder-object. You can inject this by injecting IMenuBuilder and build your own menu structure or you use the build-in adminLte-menu...
EV5.AdminLTE is the package including AdminLTE packaged as ready to use in an EV5.Mvc project. https://adminlte.io/
EV5.Mvc is a custom view engine for the latest ASP.NET MVC on .NET Core 5. Check out the live demo: https://ev5testwebapp.azurewebsites.net/