Mac Mini resolution out of range at grub and desktop enviroment

[oldfred]

From grub menu use commands to get to grub's terminal and run this. Grub may not see same video as system.

vbeinfo

Then uncomment gfxmode and change to one of values shown by command above.

[viarippa11]

Hi oldfred, I already tried that command in the Grub console. Situation is as follows:
- if I use my lcd TV as a monitor the only one resolution that seems to be supported is 1360x768
-if I boot using the HP monitor then switch the video cable to the lcd TV (since it's impossible to have video output using the HP monitor) the only one resolution displayed is 1920x1080, which is (as said) unsupported by the HP monitor (official specs say that maximum resolution is 1600x900)
...does this mean that I'm screwed and there is no solution to my problem, or the only possible solution is to buy a new monitor?
(I hope that what I've written is understandable.. Sorry me but I'm not a native English speaker...)

[oldfred]

It sounds like it is defaulting to 1920x1080, and then your monitor does not work as you posted originally.

But that is more the video driver settings. And I thought grub tried to use the system default unless you reset with gfxmode setting in grub.

Cannot really help, as do not know Mac.

[viarippa11]

That's exactly what happens: computer believes the right monitor resolution is 1920x1080, but this is not supported by the monitor. That's really weird. Any case, thank you very much for your effort.

[viarippa11]

After another weekend of testing and googling, I was wondering if perhaps this discussion couldn't be moved to another section, such as some hardware or video section. I believe this issue is not something that has to do with apple architechture, rather than correctly setting xorg and/or gdm3 configuration. This mac is very similar to a standard desktop PC: CPU, chipset and graphics are from Intel, the RAM is the same mounted on any IBM compatible machine and it mounts a standard SATA 2,5'' hard drive...

I tried to edit xorg.conf and a bunch of other configuration files but computer still defaults to 1920x1080. I think this issue is somewhat related to framebuffer, though I'm not that skilled to know how this is related to the display server. If I issue sudo fbset, the output is:

mode "1920x1080"
    geometry 1920 1080 1920 1080 32
    timings 0 0 0 0 0 0 0
    accel true
    rgba 8/16,8/8,8/0,0/0
endmode

I tried to run this command on another PC that works and the output is the right screen resolution.

Furthermore, this (https://pastebin.com/fY70UZh3) is the content of ~/.local/share/xorg/Xorg.0.log and, as far as I know, it seems that 1920x1080 is autodetected for some reason, even if it doesn't work. Obviously X chooses the highest possible but I don't know how to avoid it.