Unable to change CachyOS brightness after update, or after disabling dedicated GPU in UEFI / ‘BIOS’ settings

Potentially a silly question.

After an update, or a settings change, or something, my Lenovo laptop (16ARH7) running CachyOS (KDE) is running into an issue where its backlight commands (using the Fn keys) not only don't work, but also seem to lag the computer quite substantially, when changing brightness values.
After being pressed, a number does indeed display on the screen (e.g. 0% to 5%).
Attempting to turn the brightness down from 0% does not introduce any visual spikes of lag.

However, none of these changes are reflected in... the display's brightness.

As a troubleshooting measure for other matters, I've attempted to switch purely to my integrated graphics (by changing the relevant system UEFI setting).
It may be that brightness functionality restores when I switch back, but I wonder what the odds are?

Would appreciate any troubleshooting tips.
Tried to find some stuff online, but they usually referenced config files or tools I don't seem to have / don't seem to apply to me.

Host: 82SN (IdeaPad 5 Pro 16ARH7)
Kernel: Linux 7.2.5-1-cachyos
Display (BOE0AC1): 2560x1600 @ 1.5x in 16", 120 Hz [Built-in]
Desktop Environment: KDE Plasma 6.7.5
CPU: AMD Ryzen 7 6800HS Creator Edition (16) @ 3.20 GHz
GPU: AMD Radeon 680M [Integrated]

Thanks so much all, in advance! :))

Posting this for the purposes of contributing to an actual human network rather than a silly robot.