I have an Acer XV340CKP monitor connected via Display Port to my GPU. I also have a old LG W2253TQ that I use as a secondary display. It only has a DVI and VGA port. I have a DVI-DVI cable together with a DVI-Display Port converter to connect to my GPU, which is an Asus RX6900XT. I am running Nobara 38.
I have observed that if I were to have my Acer monitor powered when I switch on my desktop, all the monitor buttons do not respond. None of the menu buttons, not even the power button responds. When I switch off the desktop, the monitor stays on. The only way to power it down is to unplug the power cable.
However, if I were to only have the LG monitor powered when I switch on my desktop, all the buttons on the Acer monitor works.
I believe everything was working previously in Nobara 37. I think this issue probably started happening in the recent month or two.
Is this even possible, where the graphics card sends a malformed signal to the monitor and prevents the buttons from working?
DVI should not control the monitor’s actual physical controls - it does include a small non-display channel but IIRC that’s used to get the display modes info from the monitor, and potentially to transmit contrast information and the like; some monitors will prevent you from adjusting contrast if DVI sends that info for example, but it certainly shouldn’t disable the power button.
My guess would be a hardware issue - in the monitor itself - which is somehow triggered by the sequence in which you do enable the displays, and your system update being unrelated. It’s a huge guess though. One thing to try is repeating both sequences (the one that locks your buttons and the one that doesn’t) using a live CD - not a “nobara 38” one if such a thing exists, another distro. Trying both monitors on another computer would be an interesting test as well, although not necessarily that helpful (because if it doesn’t occur there, it might just mean the issue is triggered by peculiarities in your graphic card).