Finally gave in and purchased the game on Steam, I wanted to have it forever anyway and not be reliant on the Game Pass if I ever want to cancel it.
It's shocking how easy it was to setup the X55 following the simple instructions on reddit (editing the xml files in the input folder), while I could never make it work on MS Store, even when following the tutorial step by step. I do wonder why Microsoft makes it so complicated to touch anything, and it's not only for MSFS.
So for Steam, open the reddit link from irsmurf's post, view all comments, and check the tutorial by OP. It basically comes down to making copies of the X56 profile xml files, renaming them to X55, and changing the device GUID inside. Then edit another easy to find xml file to have the X56 texture displayed. Works flawlessly.