I know, for games it's creators prog or Idklt@xbox and I published 2 games with creators prog already. But I selected app not game (not enabled creators prog) and could never enable "Win10 Xbox" at the packages screen. But you can select it now. The person testing did not say it has to be a game. Just that app freezes on startup every time. 🤔 So I assume it was for the apps section on Xbox and if it did not freeze it could be published.
Would be nice to add apps created with Construct but I have no idea why it freezes on Xbox and runs fine on PC, phone and tablet.
I thought maybe there is something you need to add (reference/package) or is there any known issue with Xbox exports? I could not test it on my Xbox at home yet.