Você pode definir explicitamente a tela à esquerda da qual com xrandr
:
xrandr --output DVI-I-1 --auto --primary --output DVI-I-2 --auto --left-of DVI-I-1
De man xrandr
:
--left-of, --right-of, --above, --below, --same-as another-output
Use one of these options to position the output relative to the
position of another output. This allows convenient tiling of
outputs within the screen. The position is always computed rel‐
ative to the new position of the other output, so it is not
valid to say --output a --left-of b --output b --left-of a.