Ok this will be a long post.
First a few remarks concerning color management:
It seems to do something, but I am not sure it is the right thing. Here are 2 screenshorts. The first one is without color management and shows more saturated colors, the second one is with color managment and shows less satureted colors. Since my screen’s color space is slightly larger than AdobeRGB, the direction is correct.
But here is another screenshot:
The same screenshot is opened here in Geeqie (top, with color management) and Lximage (bottom, no color management). The screenshot opened with Geeqie should show correct colors, however, when I open this photo with vkdt, it looks like the screenshot in Lximage. I think this is also visible in this post. Now I am not sure why this is, maybe it has nothing to do with vkdt, maybe something is wrong with my color management setup. Bottom line: there is a difference between with and without color management in vkdt, but the colors seem to be too saturated, both with and without color managment. (The colors are less saturated in other color managed apps.)
Then, a question: What type of profile does vkdt want? I chose 3xGamma+Matrix. Does it like XYZ LUT profiles (e.g.; I did not test this)? Does it care about profile types?
Finally: apparently setting up color management for vkdt does not work like described in the documentation, and there might be a small mistake in the file names. First I ran the script read-icc.py, as desribed in the documentation, after I had installed the profile:
[anna@annapc bin]$ ./read-icc.py
please supply icc profile as command line argument
usage: ./col.py your-display.icc
But col.py does not exist! Is this a joke?
Finally I was able to set up color management in vkdt by running ./read-icc.py /home/anna/benq.icc.
Well so far I only tested color managment in vkdt once though, so I am not sure if the result would be exactly the same thing if I did this once again.
Second: I have information about successful compiling of vkdt on Fedora 31 and unsuccessful compiling on Manjaro and Debian Buster/MX Linux 19. Compiling on Manjaro was very easy, most packages were already on the system, and first it looked like it was a success, but when I tried to run vkdt the screen inside the window frame was just black, and there was no information about errors in the terminal. On Fedora (which I am using now) it was more or less easy but most packages have slightly different names. (I don’t know how useful this info is.)
Finally (bit off topic) dual graphics/Nvidia prime: I was actually able to install the original Nvidia 440.44 driver on Debian testing and MX 19 (which should behave like Debian Buster). Battery life is less than 3 hours on Debian testing without actually using the Nvidia card, which is not really great but better than with the old driver form the repo (less than 2 hours without Bumblebee). And during those 3 hours, the system crashed completely twice. On Fedora Nvidia prime works out of the box and batterly life is a little under 5 hours (I think this is also true for Ubuntu), but the driver is in some special repo, so it is not the “original” driver. On Debian with the old driver from the repo + Bubmblebee, battery life is longer than 5 hours. MX19/Debian Buster did not crash with the original driver, but darktable was extremely slow with OpenCL. Btw: installing the original driver was a bit complicated but not really difficult. However, I did not do anything but installing the driver. I tried that custom xorg.conf thing but it just broke my X-server (I only changed the BusID).
I think I wanted to mention one or two more things but I forgot what it was LOL
I am a such snail. I think I needed like one hour for writing this post.