Hello,
I have problems with motioneye. I use a Raspberry 3B with the Cam 2.1. it is also recognized as V42L and MMAL. When I select one of the bcm2835 only “unable to open video device” appears. The problem is that the brightness control doesn’t work. Either too dark or too bright. Auto Brightness doesn’t work (brightness changes constantly) and the setting options have no effect no matter what you select (yes I pressed “Apply” 
). When I change the resolution the (automatic) brightness from the Cam 2.1 works, but only at such a low resolution that it does not help me. So it depends on the resolution.
In the previous version I uses a pure motioneyeos everything worked fine. But together with dietpi unfortunately not. (It is possible that I used an older version of motioneyeOS there and ccrisan changed something in the newer versions?!). Do you have any advice?
By the way, with motioneye the Raspberry has a constant temperature of 69-72°C, when I uninstall it, the temperature drops again. 70°C are not very healthy for the Raspberry in the long run. But I didn’t want to connect a fan now.