24.04 - Raspberry Pi 5 with RP 7 Inch Screen Will Not Turn Off Screen When Blanking

I have a Raspberry Pi 5 with the Raspberry Pi 7 inch touchscreen. When I turn on screen blanking with Ubuntu 24.04 and it blanks, the screen changes but the screen does not turn off. Basically, the screen starts fading, but then turns a light gray and does not turn off the power. The same is true when I power off the device. The devices shuts down, but the screen does not turn off and just has the gray screen.
https://i.sstatic.net/4hKmIetL.png

https://i.sstatic.net/4hKmIetL.png
What the gray screen looks like: https://i.sstatic.net/4hKmIetL.png

https://i.sstatic.net/4hKmIetL.png
I have a separate microSD card with Raspbian bookworm on it and when I boot the device with that microSD card, everything works as expected. The blank screen is completely turned off and when I power off the device, the screen also turns off.

Do you have any suggestions for how to turn off the screen on Ubuntu 24.04? I'm a fairly new Linux Ubuntu user so I could be wrong, but this seems unique to Ubuntu and the Raspberry Pi 5 and Raspberry Pi 7 inch screen.

I have tried:

xset dpms force off -> and also different forms of this to turn off the screen, but I get different errors.
xrandr --output DSI-1 --off -> DSI-1 is returned from --listmonitors and that too outputs some error about invalid parameter.
adding hdmi_blanking=1 to the boot config.txt -> It didn't help.

Also, I noted that the screen can be turned off remotely via SSH before or after the screen blanks by setting the brightness value to 0 in /sys/class/backlight/6-0045/brightness. However, when I wake the system by moving the mouse or hitting the keyboard, the screen does not come back on.

Finally, I asked this same question at https://askubuntu.com/questions/1512...een-when-blank, but didn't get any responses so am asking it again here.