OneShot is now on itch.io (GREAT!) but i think the Mac and Linux ports should be added as well. They aren't perfect, but if we're going DRM-free we might as well be free from the hellscape that is Windows.
The actual Linux port was worked on on this repository. I used make-oneshot-linux.sh to build the Steam version of OneShot and a small modification to mkxp.pro's line 12 could make it build OneShot without Steam bindings, but the script does not install other dependencies so it will not work by itself. My old build instructions from here don't work anymore but should contain the list of dependencies that need to be installed in order for OneShot to successfully compile.
Since the Steam page offers a Linux client I was surprised to find it not offered here. That is where my expectation comes from. It's not that I want it now, but that it exists so why not offer it here too? Maybe there is a good reason.