After much research, I found the solution.To add new resolutions, you need to use the command xrandr
.
In my case I would like resolution 1368x768:
cvt 1368 768
with the output of that command used as a parameter for the new command.
xrandr --newmode "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync
xrandr --addmode eDP-1 "1368x768_60.00"
However when restarting the system you will lose these settings, to solve this you must add a script at ubuntu startup.
Create a script called /path/to/.set_monitor.sh
#!/bin/bash
cvt 1368 768 # xrandr only works in X11 sessions, not Wayland
[ "$XDG_SESSION_TYPE" = x11 ] || exit 0
xrandr --newmode "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync
xrandr --addmode eDP-1 "1368x768_60.00"
and add the following command to startup applications.
/bin/bash /path/to/.set_monitor.sh