How did you disable the LED? I mean I can disable LEDs via /proc but not in config.txt correct?
# Disable Power LED after boot
dtparam=pwr_led_activelow=off
# Disable SD card activity led
dtparam=act_led_trigger=none
dtparam=act_led_activelow=off
# Disable the ethernet LEDs - these are Pi4 specific values.
# Look in the docs for the values for other Pi boards.
dtparam=eth_led0=4
dtparam=eth_led1=4
It appears to depend on firmware or kernel but for recent kernels (recent 6.1 or 6.2) activelow is no longer necessary [1]. It seems to work on CM4.
PS: my bad I disabled the LEDs via /sys not /proc previously:
> # for i in /sys/class/leds/*; do echo 0 > "$i/brightness"; done
The required lines were different between the Pi 2 and Pi 4 I was using at the time, and the documentation was not updated (or I'd found old docs).
An exercise in trial and error.