[Debian 12] Laptop screen remains off after sleep on graphical session

Hi guys! Hope this is the appropriate place to ask this question, but here it goes.

I have a Dell Inspiron 7520 laptop with integrated Intel and ATI graphics.

Recently I've installed Debian 12 on it, using Plasma.

Everything is fine and dandy, but there's a problem; when the system comes back from sleep, or I boot up the PC with the lid closed down, the screen never comes back. The system is running, but there is no screen.

Also, it's not just a blank screen, it does not get power, no backlight, no image on the screen if I shine a flashlight onto it and look hard.

Interrestingly, if I switch sessions to any ttys, the screen comes back and the terminal session displays fine. If I Alt+F7 back to the graphical session, the screen turns off again.

In theory, every graphics driver should be installed, I have non-free-firmware in my sources.list, all the packages that the Debian documentation mentions are installed.

Don't know, if relevant, but same on both X11 and Wayland.

Any ideas?

Thanks, guys :)

Some specs of the machine:

• CPU: Intel Core i7 (3rd Gen) 3612QM / 2.1 GHz
• GPU: Intel HD Graphics 4000 + AMD Radeon HD 7730M (switchable*)
• RAM: 16GB**

*: Not sure this switchable thingamajig works, tho. Haven't really tested, the only purpose of this machine is to start OBS and begin outputting video on NDI.

**: Though 16GB is not really supported on paper I guess and had some really funky issues before, not sure what was the real purpose, the system is rock solid since the last few OS installs.