I implemented mixed Authentication for DotNetNuke ( Use Windows Integrated Authentication for seamless logon intranet logon and use Forms authentication for users unable to use Windows Integrated authentication), similar to as I did it before for my ASP.NET application . See my previous post about some problems that I had.
It is also required to promote imported from Active Directory Administrator user to SuperUser. The current DNN core doesn't support this.It only allows to create a new SuperUser.
I had to add a new link button “Make SuperUser” to ManagedUsers.ascx. More...