Let my laptop sleep overnight, after logging in to an existing plasma session, the external (DP) monitor is way too dark.
The only workaround is to log-off and log on again.
(fiddling with tools does not help)

My setup:
power-management: display & brightness: dim automatically: never
(interesting side-effect: changing the screen-brightness slider only affects the laptop built-in screen, not the external monitor)

My utility-script helps in setting the (for me) suitable config:
ddcutil --display 1 setvcp 0x10 30
brightnessctl -d 'amdgpu_bl1' set 20%

This does not help to regain intial brightness after wakeup, though

`kscreen-doctor -o` confirms my setup
Output: 1 eDP-1
        Brightness control: supported, set to 20%
Output: 2 DP-5
        Brightness control: supported, set to 30%
...this remains true even after waking up from sleep, although the brightness of the DP-connected monitor is too dark

These settings also correspond to the monitor-setup (hardware-keys). Asking my monitor-OSD/menu confirms that brightness is indeed 30%

Fiddling with 
sudo tee  /sys/class/backlight/amdgpu_bl1/brightness <<< 52
obviously only affects the built-in laptop-monitor, not the DP one

For me, this looks like plasma is doing some other kind of darkening that i cannot control on the commandline?
(any dbus commands that may help?)

Im prette fedup with the neccessity to logoff/login only to restore screen-brightness.
Yes, i can grab the plasmoid-brightness slider and pull the DP brightness all the way up to 80%, which then somehow matches my intended brightness.
This only helps temporarily, because logging off/on later remembers this setting and the DP monitor is waaay to bright (so i need to fix this with the ddcutil script above)

Something is not working correctly since plasma 6.2.0 (and still broken in 6.2.1 and 6.2.2)
any help is appreciated