I’ve had an issue with brightness control ever since I moved to Linux, on all distros (pop, fedora, now solus). The keyboard keys don’t work and neither does the slider in the system.
I was using GNOME mostly until a couple of weeks back and I used to install an extension called Soft Brightness as a workaround for this. It would make the slider work at least even if the keys still didn’t work. I’m not able to find something like that on Plasma.
Laptop: Lenovo IdeaPad Gaming 3 ARH05. Ryzen 4600H processor with AMD integrated graphics and a discrete GTX 1650 mobile GPU.
Odd, everything seem normal I thought it show some weird name in display setting, but you can try 3rd party brightness control listed here
I remember trying all this on GNOME before finding the extension. But I’ll check again, thank you