Rebooting with the dtb installed alongside the others and the line added to /boot/config.txt, fails to cause any change in behavior - the videoconsole still appears on the HDMI-out and no output (except the backlight) appears on the hat’s screen.
We aren’t very familiar with that linux kernel; does it perform as expected with the Raspbian OS? Run through the hookup guide here https://learn.sparkfun.com/tutorials/sp … ion-part-1 ( might be inconvenient, but helps eliminate board issues) and we can go from there