Okay, I finally got my camera to work. It's the DH-IPC-HDBW4631R-S, purchased off of Alibaba years and years ago, accidentally flashed with a firmware that bricked the device. I'm fine with a Chinese web UI since I can just translate the page on the fly using my browser. FWIW, the new Chinese...
Did you manage to get a dump of this firmware? I also have a HDBW4631, but I have two of them with bad firmware. Would love a file from which to restore :D
Hopefully this helps someone, but I think I found the TFTP backup tool archive.
If anyone has hot tips for recovering a DH-IPC-HDBW4631R-S purchased years ago from Aliexpress, please let me know! Still not sure what firmware I should be trying to restore.