Luna Display has added support for using an iPad with a Windows PC. The company originally offered the functionality for Macs and iPads but Apple subsequently 'sherlocked' the feature in macOS Catalina with its Sidecar functionality.
https://www.notebookcheck.net/After-getting-sherlocked-by-Apple-Luna-Display-now-allows-you-to-use-iPad-as-a-second-display-for-Windows.572281.0.html
I still don't get the "secret sauce" Luna display has, it's not the same than using an hdmi dongle and share that screen on the ipad using any software that encodes it on h264/5 at low latencies?
It probably is, but without the dongle you couldn't charge de over $100 could you? Or perhaps Apple blocks something and it wouldn't work without it.
But if Apple didn't really paid nothing to the company, it's a very bad from apple...