It’s just the kernel and virtualization stack that are custom. Dual booting is annoying as you lose access to your entire desktop environment. Want to tab out of your game and check your email client? Well you can’t unless you maintain another email on the Windows partition that you only want to use for running a game anyway. If you spend any significant amount of time gaming you just end up getting dragged away from Linux where you want to be. I was dual booting for a while and it was fine for a focused Skyrim session here and there but when I started playing an mmo that I was in and out of constantly it was very inconvenient to not have access to my Linux desktop environment while I was idling in the city for hours.
With lookingglass nowadays it practically feels like just running a windows game on Linux. I used a vfio setup for years before Linux gaming support was good and I had to switch monitors inputs and toggle my kvm whenever I launched a game and it was still better than dual booting. There wasn’t kernel anticheat back then though so i didn’t have to muck with the kernel and uefi.
With lookingglass nowadays it practically feels like just running a windows game on Linux. I used a vfio setup for years before Linux gaming support was good and I had to switch monitors inputs and toggle my kvm whenever I launched a game and it was still better than dual booting. There wasn’t kernel anticheat back then though so i didn’t have to muck with the kernel and uefi.