I've installed Ubuntu 20.04 server on an RPI4, and want to configure it to disable the external HDMI LCD monitor backlight after a certain amount of inactivity. Not simple screen blanking as shown in this answer, which blanks the screen as advertised, but leaves the backlight enabled (on my configuration.)
I'm looking for something roughly equivalent to setting the consoleblank=$TIMEOUT_SECONDS
kernel parameter as I've done in GRUB on Intel systems:
GRUB_CMDLINE_LINUX_DEFAULT="consoleblank=300"
...but it appears Ubuntu 20.04 on the PI doesn't use GRUB. And I can't edit /boot/config.txt
as is customary on Raspbian systems.
I've found this Debian Wiki page which provides some details about the Ubuntu RPI port, but I've not been able to make use of this info (yet.)