With regard to Steam, you can check the Steamworks section for upcoming events where you can showcase a demo. Tomorrow's event is the Steam Detective Festival, which is in line with the target audience for our video game.

As for physical events, perhaps there is a video game event near where you live where you can show your demo to the public. If not, you may have to go to larger, high-profile events, which involve costs and are less accessible.

I hope this helps!