08-09-2021, 05:53 AM
Did you connect with ssh -X or just ssh? On mobian the former sets $DISPLAY to localhost:10.0 and firefox starts, while with the latter $DISPLAY isn't set, and firefox fails with the same error you show. You need the GDK_BACKEND=x11 with megapixels too, and there's a few seconds of lag updating the camera image.