In the “Good Old Days” trucks had stacks because black smoke is nasty. The stacks kept the soot a few extra feet above the ground.
Today, the exhaust is very clean by comparison, and very little soot escapes the after treatment system. So, the exhaust pipe exits at ground level, generally on the passenger side of the vehicle, just ahead of the rear axles. Like this: https://www.truckinginfo.com/fc_images/photogallery/l-ajp-0507-resize.jpg
As for the hanger thing, that might be a short wave radio antenna. I’m not sure, but it looks like it to me. Maybe the guy is a HAM radio operator.