Microsoft dives into the handheld gaming PC wars with the Asus ROG Xbox Ally
Microsoft dives into the handheld gaming PC wars with the Asus ROG Xbox Ally

Bespoke handheld interface hides the desktop while offering access to “all Windows games.”…

This will probably be the biggest competition the Steam Deck has within the handheld PC space.
Most noteworthy is that windows is finally focusing on providing a decent handheld experience, including booting straight to a controller friendly interface, and reducing background processes for better fps and battery.
Edit: The handheld Xbox UI will.come to all windows PCs, but it's not clear if the reduced performance bloat version will be available. It sounds like only Xbox branded devices may get the full benefit of optimized windows.
It's also the ugliest handheld PC yet (imo), but I can appreciate that they're pushing for comfort over looks.