In the past, problems with non-playing of video content in Firefox have been reported, with suggested fixes. I am running Manjaro in KDE Plasma on a Raspberry Pi 4B, and the latest upgrade results in Firefox not playing video content. Chromium seems to have no problem.
The fixes suggested previously involved editing items in Firefox’s Setting, but they don’t appear to apply to Firefox 116.0.1 (64-bit), so I’m at a bit of a loss to see how to proceed. Any advice would be welcome, as Firefox is my preferred browser.