Yep, the input cover controller is indeed orthogonal! There, I’m reusing the original matrix, and I’ll possibly be doing QMK too.
Now, I’ve done a thing that could interest you: Input connector shim - for power switch, USB 2.0 and LEDs if you need an internal USB port, at the expense of losing the fingerprint sensor (which can then be re-added using an internal USB hub). I’m also looking at tapping the USB port at the E-key M.2 slot - which is not utilized if you’re using an AX201 WiFi card (as opposed to AX210), but that project’s physical aspects are yet to be developed.
If you’d like to have raw connections to the original matrix, without Elite C, I can do that too! I’ve started doing an adapter for that, taking the input cover connector and breaking its connections out, but haven’t had a reason to finish this project yet - if you’re interested, I can revisit it for my next PCB order, to be completed in a month-two. Then, an EC firmware mod will indeed be required, unless you’d like to repeat the original wiring (you’ve likely seen it here already). There’s 8 rows and 16 columns, as you might’ve seen, and my intention is to break all of these out into a hand-wiring-friendly form-factor.
If you plan to reuse the keyboard FPC, you could also make an adapter for the original keyboard connector and leave it at that: Reusing Keyboard after Replacement - #8 by DHowett If you’re interested, I could make an adapter for this, but an online-store-bought FPC breakout should work too if you can find a suitable one.