I add my vote for Linux support. Preferably as an open source driver. I like to tinker with my PC and the software that runs on it. It's harder to do on Windows. As a benefit, Pimax can get external contributors to help improve, find and fix bugs in their software. I don't own a Pimax4k, but it seems that the software layer is still work in progress, so I'm a bit worried about that side of things for the 8k (I'm a backer).
Alternatively, providing technical refs for the hardware to help implement a driver is good too.