Some good news and some bad news.
I finally succeeded in upgrading the firmware on my NVR, but not without some good scares. I have the firmware .bin file stored on my NAS. I copied this onto a USB thumb drive thinking I would have to use it in the NVR. Turns out I just point to the file on my computer. So I started the upgrade by pointing to the file on the USB drive on my Linux machine. It uploaded, and as soon as the "updating" message appeared, there was a dialog box that said Upgrade failed, and asked to restart or not. The browser was hosed at this point and I could not respond. Hmph!! Must be lack of linux support. Tried it on a Windows 10 Pro machine with the same result. Figuring "What have I got to lose?". I tried again and pointed to the .bin file on the NAS. IT WORKED!
My initial reaction to the new firmware is mostly good. From Firefox, I can view my cameras without plugins, or anything. Just as long as I don't want to see more than 4. I have not found a way to set up different viewing panes like for 8 or 16 cameras at once. Same goes for playback. No more than 4 cameras, and you cannot sync them. I have not played with it too much yet, so there might be a way that I just have not found yet.
Now the bad news. At least for me. I also have an older NVR that is the same model. That one, I am unable to upgrade, but it has a problem anyway. I am thinking the onboard eeprom, or whatever is used to store settings, has failed. When I go through the initial configuration, apply everything, backup the config, and reboot, I have to go through it all again because nothing was saved. Crap! One last question for this one. What filesystem is used, and how do you format it? EDIT: btw, the firmware on this one is 3.210.somethingsomething.