4k HDR too dim/dark

The /etc/rc.local file will run on boot, so having

echo "444,10bit" > /sys/class/amhdmitx/amhdmitx0/attr

in rc.local will do the same thing on bootup as running

echo "444,10bit" | sudo tee /sys/class/amhdmitx/amhdmitx0/attr

from the command line.