I installed motioneyeos-dev20201026 clean on a PiZero.
I used a Tiga USB dashcam for my camera
I selected it (first one listed in
Camera Type Local V4L2 Camera
Camera Tiga
Under Camera1, Video Device, Camera Device shows
/dev/v4l/by-id/usb-Generic_TIGA_Device_20160418V1.000-video-index0
and is working normally
If you have a spare SDCard, you can try this. (clean install)
You can also delete all cameras and re-create it (trasdhcan icon next to camera name)
There are instructions (or used to be) over on motioneyeos github on how to make the OS read/writeable, and delete the config files.