Just to stave off anyone else coming in and going “ackshuallee”… it’s true that you could technically do that with libreELEC. It’d be a fool’s errand of using SSH to get to the terminal and install all the programs and dependencies, and you’d still need some way to do arbitrary terminal commands from the kodi menu (I think there are plugins for that and for launching arbitrary programs though).

I played around with that myself for a few hours and gave up.

I’d love something actually good, but the closest you’ll get probably is running Kodi or whatever media frontend you want on top of a stripped down “normal” OS, with a separate frontend for games/programs like HyperSpin. Find a way to launch one from the other and you’d be set.