The original X1 OS was based on 8.1. Since the release of win10, they've updated the X1 OS to be based off of win10 for better integration (UWP, dx12 compatibility on x1, and a few other things if i'm not mistaken). Let alone the fact Microsoft isn't as restrictive as Sony or Nintendo when it comes to homebrew, so there isn't a need to really hack Xbox. Whether or not someone has attempted to run a win10 environment on x1, I don't know but I don't think there would be much sense to.
Maybe it's just me, but I don't see much point in getting another OS running on the switch. I get that there is already developed Linux emulators and whatnot, but in time all that will come to the switch natively.