in settings > power management > display and brightness theres a slider and a checkbox, if the checkbox is checked then kde should set the brightness to whatever that is on login, im assuming otherwise it just has a default value to fuck with your mind
@nellePoint It was enabled and set to 100% on mine, but I do believe the brightness thing is fucked
it has happened to me before that I forget to set it to 100% again, after like 3 hours of using my desktop it randomly changes to 100% and the monitor entry disappears from the brightness menu
@nellePoint it might just be the monitor having a shitty interface on the kernel, it doesn't even show up on my windows partition to change the brightness so i have to do it through the OSD