Hello
I have a 1440p (QHD, 2560x1440) monitor, but whatever I tried it was always giving me 1080p (1920x1080). I'm using Armbian 24.8.1 Noble Gnome and the resolution settings are in the Displays system panel.
I noticed people who had similar problems on the Rock5b, the suggested solution did not work, but hinted to dtb files. After examining the /boot/dts tree of Armbian I found 3 files:
/boot/dtb/rockchip/overlay/orangepi-5-plus-hdmi2-8k.dtbo
/boot/dtb/rockchip/overlay/rock-5b-hdmi1-8k.dtbo
and /boot/dtb/rockchip/overlay/rock-5b-hdmi2-8k.dtbo
You can decompile the object file with the dtc command from the device-tree-compiler package:
dtc -O dts /boot/dtb/rockchip/overlay/rock-5b-hdmi1-8k.dtbo
This is mentioned:
Description = "Enable 8K output on HDMI1.\n8K cannot be enabled on HDMI1 and HDMI2 at the same time.";
So, I added the overlay in the /boot/armbianEnv.txt file, just add
user_overlays=rock-5b-hdmi1-8k
and the following commands:
sudo mkdir /boot/overlay-user
sudo cp /boot/dtb/rockchip/overlay/rock-5b-hdmi1-8k.dtbo /boot/overlay-user
Connect your cable to HDMI1, reboot and set the 2560x1440 resolution in the Display setting. QHD is working perfectly!
So, the dtc says 8k is possible too, but you will need an 8k monitor of course. I guess 4k will be working also.
The orangepi-5-plus-hdmi2-8k.dtbo did not work for me.
Regards
Philippe