What is the recommended way to grant STAC 3.0 access to a subset of STAC users?

We are installing RC1 this week and inviting a limited number of power user to start using it and collect feedback. By default, any users with rights in 2.x can log into STAC 3.0.

We tried using Windows Auth, but that immediately broke STAC 3.0 Beta home page, even with allow=all.