Since Jolla is linux, it should be possible to run steam on it. Imagine a future version where we can hook up a vidock to it and use the moga game pad and run the steam app on it with a jolla desktop UI with maybe a bluetooth mouse.
So your phone would replace a full desktop and maybe your laptop. You'd just be a little underpowered with the CPU for high end games but since you are hooking up to a vidock you are fine on graphics and can always upgrade it and you are running linux with a BT mouse.

Also it seems you need to install something called android compatibility on your jolla phone for certain android apps to work.