HI.
I have a projector that i cant change the screen size, but… i was using Android TV, and there you can change the size of the screen. Now, im trying to use a computer with Manjaro to acomplish the labor of the Android TV.
But… how i can change the screen size?
Thanks.
Hello @9acca9 
You can use xrandr when using xorg on Gnome, if the session type is wayland, then there would be no other way than modifying the EDID of the monitor.
xrandr --fb 1920x1080 --output VGA
This will create screen which should fit the monitor. If it is larger it will be outside of the visible space.
More info: man xrandr