Luna Display's PC-to-Mac mode lets you use your Mac as a secondary external display for a Windows PC with both 4K and 5K resolution supported natively right out of the box.
Amazon Luna
Amazon launches early access to its new Luna game-streaming service on iOS and macOS
Luna, Amazon's new cloud-based gaming service, is available starting today across a variety of platforms to a small set of users in the United States as part of an early access test.