I’ve read that the Halo Infinite campaign supports xbox play anywhere (the game in the xbox pc app also has the XPA logo). I’ve purchased the game on disc for the xbox, but even after installing it and signing in with my live account, the PC is telling me I need to buy it again when I select campaign from the menu.
When you get it working just be really careful not to sign in to two devices at the same time same account - you can easily lose your campaign progress to a vanished or corrupt save.