Did you replace the ffmpeg library that came with your new NWjs with a pre-compiled version that supports modern video formats? What you need to do is to download the appropriate ffmpeg.dll (ffmpeg.so if you use Linux) from the site associated with the link below and use it to replace the one that comes with your new NWjs wherever that is (game folder for Windows and swiftshader directory for Linux).
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The one that comes with NWjs doesn't handle some of the new video versions and you need to replace it with one that does.
Just wanted to come by to thank and highlight your post. I recently dumped Microsoft and went over to Ubuntu. Unfortunately, this is one of those games that, even with the Linux build, refuses to work right out of the box. You need to run it through launcher-fontcache.sh and even then the terminal would spit out a ton of errors while running it.
I swapped in the HD movies in place of low quality ones, but the accompanying 1.04 nwjs updates completely bricked the game. It refused to start entirely. I then grabbed the latest 1.04 from nwjs website and while the game started booting cleanly without any errors, it completely froze with a black screen when trying to run the dev logo after the first intro message.
Thankfully, I found your post from 2 years ago, and swapping in the ffmpeg file did the trick! Thank you for that. I love Linux, and I'm glad it has come a long way since decades, but it still makes you fight on a lot of things xD