Just a quick update that I successfully compiled 4.21 UWP last night and managed to run the 2D Sidescroller Template and Blank 3D project on my Series X, abeit with a weird white/blue startup screen before they started.
I couldn’t run from the UE4 Editor as my console doesn’t appear/can’t be added in Device Manager despite there being no user/pass and other engines connecting to it fine, but building an .appx and manually installing to the console worked fine.
Also the FPS Template doesn’t run and gives a “Video Driver Error” so there’s something in there that it doesn’t like but I didn’t have time to investigate what - and nothing at all ran until I made the changes mentioned in the setup guide regarding changing to “Shipping” and ticking “Use Compressed Packages”.
I also needed to use the “4.5.2 .net retargeting pack” and not 4.6.2 as mentioned in the setup instructions for VS, it gave an warning about it when loading the project so I went back and installed 4.5.2 which it asked for and it was all plain sailing from there.
Will try later engines when I get time as it took a while to compile but it seems that 4.23 might be the max and even then only if your project plays nice and doesn’t require whatever it is that causes problems.
Thanks for the information @ShadowStar_Games