I have the Moonlander and am a big fan. I haven't taken real advantage of the open-source firmware other than customizing the layout so that is is as close to a traditional layout as I could make it, given the physical layout of the keys (this mostly has to do with where you put the backspace, delete, enter, |\, control, arrow, and other keys, not the actual letters).

It's well built and looks super cool, but the real reason I got it is because it encourages a more upright, shoulders-straight/non-hunched over position. I think regular split keyboards do a good enough job of taking care of wrist issues / carpal tunnel, but only these can really help with overall back/shoulder position.