as the title says the backlight on my Chuwi Freebook doesn’t go above 50% in either Plasma (Wayland or x11) and Hyprland (wayland).
My /sys/class/backlight/intel_backlight/max_brigtness returns 640, but seting brigtness to anything above 320 doesn’d change the backlight value at all (IRL).
afaik you can’t modify max_backlight directly so I hope there is a workaround for that.
hey how are you, I have the same model and I also use an environment with wayland, I had your same error but to modify the brightness I had to use the “light” application I downloaded it in the archlinux aur, after you install it it is used with the light -S command and then the brightness number you want to use, I hope it works for you 
You can also ask chat gpt how to use the light application in case you want to delve deeper into the topic lol
Already had this program on fedora, and it is no use as it can only set current brightness and set minimum brightness where need to set maximum. It’s OK thanks for the help, and I guess I will just live with this annoyance.
Cheers!