Stange flickering of the whole session, and periodic dimming of the display's backlight: Acer nitro 5 (ryzen 4000 + nvidia)

  1. On 54, sddm fails to start, systemctl status: sddm crash linux54 - Pastebin.com
    On 59, the problems are the same as 58.
  2. when I try to set the refresh rate of the laptop display (after boot when the external display is connected it is already set to 60hz [IIRC that’s because Xorg can’t mix refresh rates? is that right?]) when I set it up to 144 nothing seems to happen, but when I set it back down to 60hz it gets messed up: Imgur: The magic of the Internet
    the second monitor is not messed up, and I can use t to set the laptop display back up to 144hz, that fixes it
    although I suspect it’s lying and when it says 144, it’s not actually 144, at least when the external monitor is connected.
    When I tried to change the resolution of the laptop display it just turned off, and I needed the second monitor to disable and then re-enable the laptop display in KDE’s Display settings.

the flickering is sill there after changing the refresh rates about.

I did unplug the second monitor from the power outlet yes.