There’s an option, but it doesn’t seem to do anything; grep --ignore-case --recursive depth /etc/X11/xorg.conf.d
finds nothing, and
$ grep 'Using .* bits' ~/.local/share/xorg/Xorg.0.log
[ 2544.878] (II) AMDGPU(0): Using 8 bits per RGB (8 bit DAC)
The X server parts of my configuration:
xserver = {
defaultDepth = 30;
desktopManager = {
gnome.enable = true;
plasma5.enable = true;
};
displayManager = {
defaultSession = "gnome";
gdm = {
autoSuspend = false;
enable = true;
};
};
enable = true;
layout = "us";
libinput.enable = true;
xkbOptions = "compose:caps,terminate:ctrl_alt_bksp";
xkbVariant = "dvorak-alt-intl";
};