Learn Turkish
Connector line 1 and 2 each drive LEDs via LV07(Z7) buffer clearly.
3,4,5 and 6 control rows with LVC138 and it seems to drive lines through 5 buffers of LV07(Z1). So the matrix has only 5 rows, not 8?
I guess 7,8 and 9 lines select columns to sense with two LV4051 via LV07(Z7). If I'm correct 2,4,6 of LV07(Z7) will be connected with 9,10,11 of two LV4051 in parallel to select column input from matrix.
Namely you can select 16 column lines with signals 7,8,9,10 and 11 from daughter board.
I don't know why they need to control AD5258 from controller. Need to read datasheet and know how to use that chip. HHKB has no control of its potentiometer.
Except for potentiometer it looks like you can control with same method as HHKB.