Ya bro I got the same issue, I'm running a Ryzen 7 5800x, Asus Tuf x570 plus WIFI, and NVidia GTX 1660 Super and no matter if I tweaked with the local hive in Regedit or anything my HDR SAMSUNG always lists as monitor 2, even when I switch up the HDMI and display cables it always wants to put my Monitor I designated as monitor 2.
I ended Buying Display Fusion through Steam and complement absolutely love Display Fusion it's going to be a must have install software for good. and alongside another program off steam when you use both display fusion and Wallpaper engine, they seem to complement each other perfect and wallpaper engine is a rabbit hole of a theme software u should def check them out.