The StatStuff videos are hosted by Vimeo.com which uses HTML5 player in Firefox. https://statstuff.com/about/misc-information/video-troubleshooting

Go to https://www.youtube.com/html5/ in Firefox on Linux as all checkmarks should be blue. If not then you may not have packages like FFmpeg installed to fully use the HTML5 player. You can also check with videos on https://www.quirksmode.org/html5/tests/video.html

I checked on the Youtube reference page and the only unchecked formats were H.264. The addons on Firefox mentions that OpenH264 from Cisco will be installed shortly but it does not seem to work. On the ffmpeg webpage recommended the installation of RPM Fusion. I installed it in case I need something. Please advice.

H.264 playback depends on hardware and operating system support.

All are ticked for me in Win10 and a AMD HD 7000 series Vid Card = a R2

Suggest you work on your Video Card Drivers and search all the Linux sites for info to get yours working or Linux forums to see what they have to say on this issue.

Please let us know if this solved your issue or if need further assistance.

IF you are using Fedora you should go to https://rpmfusion.org and select the appropriate package. Then go to Activities>Software and write codecs. You should install all the Gstreatmer codecs. There might be one Gstreamer codec for H.264 that seems that is not installed but when you click to install it says that it is. Leave that codec as it is and install the rest. You should not have a problem afterwards.

Gstreamer has not been used for a long while now as FFmpeg has been used instead for the HTML5 player.

James said

Gstreamer has not been used for a long while now as FFmpeg has been used instead for the HTML5 player.

I was unaware of that, but I reach RPM Fusion from the ffmeg.org website. When you press download, at the end of the Linux list is the link for Fedora and Red Hat packages. That link leads to RPM Fusion.