David Phillips That stubborn person/guest who won't use the app specifically designed to solve that issue gets relegated to the HDMI cable ingress with the mutliple adapters on a ring. Or you install a wireless presentation device on the HDMI ingress if you are inclined to spend more money. (AirMedia, Solstice, Clickshare, etc.)
How does one do non-Teams meetings in any other type room? They have to use something regardless of what the default functionality of the room is, right? The point is making the experience the same in every room regardless of whether there are remote participants or not, multiple presenters or not, guests or not. It makes support and training much simpler and more economical. If one has to do a WebEx, Zoom, GoToMeeting, etc, they use they BYOD device hooked to the HDMI ingress then use the SIP extension assigned to the MTR device for audio. You get content sharing and the room mics and speakers that way. No camera.
If you cannot forego the camera, one can install a USB sharing switch like the Iogear GUS432. (I tested it, works fine swithching the room USB audio/video between a laptop and the MTR device without locking devices up)
Our users have accepted this arrangement and prefer it to having more choices in the room or having dissimilar rooms. We are moving to only having a few specialty rooms to accomodate specific workflows that require more than simple content sharing, audio calling and video calling that the MTR gives us rather than having everyone room cater to every workflow.