Although I'm just speculating since the demo of Chapter 1 (as in Chapter 1 is not even complete yet) includes Windows, Linux, and macOS. Therefore, it should be likely.
The itch.io version of Project Kat is the same one as the Steam version, I sent both image. The itch.io download and the Steam recent update are both v1.4.1. Hence, Project Kat is also on Windows, Linux, and MacOS resulting in that it isn't only on Steam.
