Landscape mode + HDMI out?

I'm using an iphone as a makeshift webcam for my video calls. The device flow is iPhone -> Lightning to HDMI adapter -> HDMI/USB capture device -> MacBook. I would like to use the clips app to capture video and overlay with mimoji, scenes, background images. This actually works really well except that the HDMI output is always output in portrait mode and when I rotate the device it rotates the video on the phone but the output is 90 degrees sideways in portrait. Is it possible to have the HDMI output rotate to landscape? Is this just a bug?