G15 5515, unable to change brightness

So I have a G15 5515 Ryzen Edition with Windows 10. Been having this problem for like two months now and it's really getting on my nerves.

I cannot change the brightness from 100% to anything else, be it the keyboard, settings or even Windows Mobility Center. Weirdly enough, when moving the slider to 0, the colors get oversaturated. I don't know if this is a hardware problem or it's just some software issue.

I looked at this post where I then installed the latest NVIDIA driver, but this only fixed the oversaturation issue.

https://www.dell.com/community/Inspiron/G15-5515-brightness-keys-and-slider-not-working/td-p/8300621

Any help? Thanks in advance!

Edit: I don't know if this is relevant but this happened after my laptop was connected for like 3 or 4 hours with an external monitor. I then unplugged the HDMI cable while it was still in extended display mode. Oh, and just now I uninstalled the monitor and restarted the laptop, which did nothing.