On the O6 box it says that the HDMI port is “supporting up to 4Kp60 display output”.
However, I have not been able to get it to output anything above 1920x1080 (using the
official USB Debian live image).
I’d like to be able to use the monitor’s native resolution of 2560x1440 like I can with other computers
connected through HDMI, such as the Mac Mini M4pro.
Is this something that is supposed to work now, or are we waiting for driver improvements?
HDMI resolution
I have two monitors connected simultaneously, one at 1920x1080 and one at 3840x2160. I read somewhere that only having one resolution supported can be a symptom of the graphics driver not being properly installed. Do you have the kernel module linlon_dp loaded? And what’s the output of “xrandr” ?
I actually got 2560x1440 working with the USB live image now; turns out it was a cable issue… 
When using an upstream kernel with the EFI framebuffer driver I get a weird behaviour though:
The signal to the monitor is 2560x1440, but the framebuffer is just 1920x1080 which gets upscaled to 2560x1440 when sent to the monitor. I guess this is a limitation of the EFI interface and that I need to wait for the linlon_dp driver to be upstreamed…