A police detective visited me today to obtain video footage that my Starlights picked up from a theft across the street. It was a bit embarrassing seeing me struggle with these damn Dahua/browser issues trying to save some footage to a USB stick. I had to lug a monitor and keyboard into my security closet to connect to the NVR just to be able to get a fully functional playback interface with a timeline that worked. I finally got what he needed and even converted it to AVI for him. He was most impressed with the image quality given the distance and darkness. Thank goodness he was so patient.
Anyway back to the OP, I've had the best luck using Chrome's IE tab to access the cameras or NVR for configuring them, with the huge exception that the bottom green timeline to advance to a specific time period is not visible. Everything else works OK but that.
So the problem I was having with not being able to run webplugin.exe with FF ESR was that I was using the 64bit version. I just replaced it with the 32bit 52.7.3 ESR and now when accessing the Dahua NVR, before I can even login, I am prompted to allow running NPMEDIA.DLL. A quick check of that DLL indicates that it is "suspicious" (malware), so I selected "continue blocking". Oops, now the NVR won't even let me login. Do you all really trust these DLL's, Plugins, ActiveX? Is Dahua ever going to modernize their browser interface for displaying video?