We are in the initial steps of installing Portal.
We have a server we are installing Portal on and at no point in any documentation does it state that IIS is even required? I've been working with ArcGIS for Server for years now so this is a huge leap forward and the documentation is anything but straight forward.
From what it looks like, we need IIS on the server with the Web Adaptor. Other than that, Portal can exist on a server without IIS.
Does anyone have anything that might help me on this?