In Microsoft's case, UWP on XBox doesn't count as it is castrated to the actual OS capabilities, and hasn't been updated for a while and most likely it won't.
In some version of Visual Studio the SDK can be downloaded from within the program.
XDK: https://docs.microsoft.com/en-us/gaming/xbox-live/get-starte...
The XDK (aka HDK) includes physical hardware and is intended for more demanding games.
Sony SDK: https://www.companyregistration.playstation.com/SCEInternetA...
The Sony SDK and HDKs are available to registered partners only, though registration is free and the SDK (but not the HDK) is free to all partners.
In Microsoft's case, UWP on XBox doesn't count as it is castrated to the actual OS capabilities, and hasn't been updated for a while and most likely it won't.