It's now possible to install and play Emulators on the Xbox One with "Dev Mode" (These Emulators were available on the Xbox Store but were pulled after a while, hence the need for "Dev Mode" to be activated..
How Developer Mode works
Dev Mode costs $20 or is free if your a student (with a student E-mail account) You can get More information on how to activate Dev Mode here: https://docs.microsoft.com/en-us/windows/uwp/xbox-apps/devkit-activation
Now on to the Good Stuff
What currently works on Xbox Dev Mode:
Nesbox is a multi Emuator that supports NES (.nes), Sega (.gen .smd), Super Nintendo (.smc), GameBoy (.gb .gbc .gba)
Retrix is a multi Emulator that's ported from Retroarch (so expect more supported Cores) that supports: NES, Snes, GB, GBA, SG-1000, Master System, Game Gear, Mega Drive and Mega CD. (and hopefully soon PS1)
PPSSPP is a PSP Emulator that runs very well (most games run fullspeed)
There's also a N64 and PS1 emulator too but the authors require you pay for them
All apps run in dev mode are in the format Appx, so other Appx compiled to run on Win 10 should be installable on Xbox Dev Mode Too.
If you want more info or if you stuck anywhere you can get help from: https://gbatemp.net/threads/how-to-install-retrix-retroarch-libretro-port-for-xbox-one.474453/page-8#post-7415449