I am surprised to see that there is no link pointing to Komar's excellent article on
How to make a keyboard - the matrix at the beginning of the thread. There are lots of great info in this thread, especially about laying out stuff in kicad, but to me there is no point in knowing how to put the dough in the pan if you don't know how to make it from the base ingredients. I did not find many articles covering the fundamental principles behind keyboard designs, so that makes this one even more welcome.
If anyone knows of similar, thorough articles about matrix design, controller (Teensy ?) programming and perhaps LED matrix/controller stuff, it would be great to share them here. Unfortunately, it's easy to find close-ups of custom PCBs with enough bokeh to prevent anyone from learning anything from the showcased design (in other hobbies, reverse engineering is a common and not frowned upon method of learning), but it's harder to find genuinely instructive content like Komar's article about keyboards. But I'll keep searching
[just to be clear, this is not a slight towards anyone (small scale sellers or fellow DIYers), it's just that I'm surprised to see so many custom keyboards projects, and yet the information seems a bit scarce (at least compared to what I see in other hobbies), despite the numerous build reports.]