I have a DSLR with video capability, so I bought a HDMI to USB input dongle. Works fine with MS Teams, but for some reason Zoom selects the lowest possible reso

I have a DSLR with video capability, so I bought a HDMI to USB input dongle. Works fine with MS Teams, but for some reason Zoom selects the lowest possible resolution setting which has the wrong aspect ratio and makes me look squished. There's no setting in Zoom to get it to select a different input video mode, and I haven't been successful in getting V4L2 to pretend that the wrong video mode doesn't exist. The advantage of using a DSLR with a nice big lens is that you can open the aperture up wide, and you'll be the only thing in focus.