my app that is live on the store but is not available only to iPad Pro M1 owners. It works in simulator including iPad Pro m1 sim. It submits and reviews with no problem. Only iPad Pro m1 owners get the message. They also get the message in TestFlight. "isn't compatible with this device".
Apple support by email says they can't determine the problem, a particular user could try to raise an issue, but I can't.
I rebuilt and resubmitted with latest Xcode. Same problem.
Not sure what else to try or how to try it. My understanding is if IOS > 11.0 is set in Xcode, it should be available to any IOS 11.0 device. iPad Pro m1 is IOS 15.x of course.
Answering myself. The device capabilities required in plist.info specified GPS required and I never realised that all Wifi iPads even latest, do not have GPS.
The app store and TestFlight do not tell you the REASON the app is blocked for install, just that it is.
A bit surprised apple developer support could not easily see this was the cause.