Unless it’s a dumb TV you can just install the Steam app on your TV and avoid Sunshine and the Pi all together.
On top of that, the Steam App is a bit janky, so much so that I just hauled my gaming rig out, plugged it directly into the TV, set Steam to launch at start-up in Big Picture Mode and bam, good to go.
Can't wait for the Steam Machine though...
Also the way Steam encodes the stream is reportedly lower quality than Sunshine. This has been a thing for years.