VEVOR Sewer Camera, 164FT 4.3" Screen, Pipeline Inspection Camera with DVR Function & Snake Cable, Waterproof IP68 Borescope with LED Lights, Industrial Endoscope for Home Wall Duct Drain Pipe Plumbin

I did use it for that and was quite happy with it. The cable is not terribly stiff so you may need to tape the end of the cable to a snake of some sort if you are feeding in to a longer distance or a partially clogged pipe.

Yes, me. I bought the VEVOR Sewer Camera, 98.4ft/30M 4.3" Pipe Drain Inspection Camera with DVR Function & Snake. I am very happy with it and it works great. I gave my drain a good inspection after I unblocked the clog first. However, if your main line is all clogged and backed up, the camera might not show you a good video on the screen. In that case you would have to snake out the drain and unblock the clog before using the camera.