It is also possible to make the monitor brightness show up as a normal system setting by using a kernel module. The other thing I read when I did this is that monitor flash memory that stores the settings, like brightness, is often particularly bad, having only 1000s of cycles. If you do use this, just keep that in mind
Edit: i checked again and 1000s of cycles is low. 100s of 1000s is more reasonable, but could still be reached fairly easily within the monitors lifespan if frequently adjusting
The kernel module is ddcci-driver-linux
This is the Reddit post I read. It links to a Hacker News forum post as well that discusses it. Really it shouldn't be much of a problem unless you're using dynamic brightness that is overzealous