No they do not connect to ground and no, they do not connect to all Y lines. An individual button connects to one X and one Y line and it has a diode in series.
Hello,
So then a button circuit path would be:
xo>diode>button>yo x1>diode>button>yo x2>diode>button>y2
xo>diode>button>y1 x1>diode>button>y1 etc..
etc.. etc..
Can the diodes be after the buttons?
TY for assist Guido