Before you return your card, keep in mind that gphoto2 will only receive at the resolution of your camera's display. For example, my camera can shoot at 4k, but gphoto2 only provides 640x480p.

Additionally, many camera features (flicker-reduction, electronic shutter options) are unavailable through this method.

This is really equivalent to a camera remote preview video, not intended to be used for actual video capture.