I've been fairly busy at work (as in the job that pays the bills) but I ordered a knob for my lerdge X and soldered it in. Lerdge X and K pin mappings seem to be right, though since I'm not remotely using all the functions I can't be certain everything works (led strips? No. Probe? No. Motor fan, etc? Hahahahahaahaha) My test printer is literally a Monoprice Mini I wired adapters up for (see my other project for hacking on that).
I'll start a PR to Marlin main to add X and K boards soon.