I do not have a Pi 4 but on my Pi 3 Model B I have this:

sudo nano /boot/config.txt # Disable the PWR LED dtparam=pwr_led_trigger=none dtparam=pwr_led_activelow=off # Disable the Activity LED dtparam=act_led_trigger=none dtparam=act_led_activelow=off crontab -e @reboot echo 0 | sudo tee /sys/class/leds/led1/brightness

You can try this to see if the above cron entry works (before rebooting):

echo 0 | sudo tee /sys/class/leds/led1/brightness

Perhaps some stuff does not work or does the same, but both the power LED and activity LED on my Pi are off in the end.
Btw, on my Pi 3 Model B Plus, only the /root/config.txt line are needed.

Concerning the LAN LED’s I found following:

# Disable LAN-LEDs on Raspberry Pi 3B+ dtparam=eth_led0=14 dtparam=eth_led1=14 # Disable LAN-LEDs on Raspberry Pi 4 dtparam=eth_led0=4 dtparam=eth_led1=4

Good luck!