If you can find a terminal command or script that reliably changes your screen's brightness in hardware, you should be able to make your system automatically change its brightness back to 100% after every wakeup. Here's a really long list of techniques for changing screen brightness from the command line: How to change LCD brightness from command line (or via script)?
Once you find the command that works for you, turn it into a script like this (adapted from https://unix.stackexchange.com/a/404010):
#!/usr/bin/env bash
case $1 in
post)
plop your screen brightness fixing command here
;;
esac
Obviously, replace the placeholder accordingly. Then save the script as /usr/lib/systemd/system-sleep/brightnessfix.sh
(assuming you don't already have a script named brightnessfix.sh
in the /usr/lib/systemd/system-sleep
directory), and then run the following sequence of commands to set the permissions properly:
sudo chown root:root /usr/lib/systemd/system-sleep/brightnessfix.sh
sudo chmod 0755 /usr/lib/systemd/system-sleep/brightnessfix.sh