Works for me. see screenshots Show us what you're seeing when you try to play a video. Also, provide a link to the video(s) that are not working for you. https://www.floracing.com/live/27148 What OS? What desktop? X11 or Wayland? Make sure you have current ffmpegs and libav installed.

Operating System: openSUSE Tumbleweed 20220719 KDE Plasma Version: 5.25.3 KDE Frameworks Version: 5.96.0 Qt Version: 5.15.5 Kernel Version: 5.18.11-1-default (64-bit) Graphics Platform: X11 Processors: 4 × Intel® Core™ i7-4810MQ CPU @ 2.80GHz Memory: 31.0 GiB of RAM Graphics Processor: Mesa Intel® HD Graphics 4600 Manufacturer: Hewlett-Packard Product Name: HP ZBook 17 G2 System Version: A3009DD10303

To make sure you fully support HTML5 players, make sure you have packages like FFmpeg installed.