A depth camera can give rough finger height[1], and multi-camera care and kludgery can do even better, but, that last little bit, of high-speed high-reliability millimeter-ish is-it-touching-the-key-yet/still-or-not contact determination, is something I've not seen well addressed.
Given this unicorn-like keyboard, I wistfully note that having pressure sensing would be very nice too...
FWIW, I also note one way a company can easily support linux, often overlooked, is to provide only an as-is unsupported binary-blob library with any secret sauce, and leave it to the community to link it, wire it to IO systems, and deal with OS variants. The payoff, for a product throttled in part by community innovation and/or adoption bootstrap, is that while linux is often a small market, it's a highly-disproportionately innovative one. For this keyboard, the envisioned market may be mostly gaming, and thus mostly Windows. But it might be a youtube "look at my neat hack" video, which prompts some game dev to support it.
