Use this resolution:
Width: 600
Height: 270
(this works for most of the phones. But to make your screen adapt to the bezel-less phones, add the following function)
Add this function to your global script :
func SetDisplay():
var viewPort = get_node("/root").get_child(1).get_viewport_rect().size
var camera = get_node("/root").get_child(1).find_node("MainCamera")
print(camera.name)
View_port_scale = 600/viewPort.x
camera.set_zoom(camera.get_zoom()*View_port_scale)
print(camera.zoom)