It is related to the Samsung screen. There‘s a kde bug since Plasma 6.2 where this is happening. Long story short: disable ddc (look up your plasma-powerdevil.service file (mine was in /usr/lib/systemd/user) and add Environment=“POWERDEVIL_NO_DDCUTIL=1” to it. Save, restart powerdevil (or reboot) and it shouldn‘t happen anymore.)

See https://bugs.kde.org/show_bug.cgi?id=494522 for reference. Hope it works

Had something similar with ASUS…never again