If you have manually enabled video hardware acceleration in Firefox (it is disabled by default), it stops working properly in Firefox 98 and later.
It seems that those videos, which are possible to accelerate with your hardware, will not start playing at all and a browser crash dialog will appear, if you have an AMD graphics card, or will play, but unaccelerated, if you have an Intel graphics card. (Nvidia cards owners are probably not able to use the acceleration at all, so they shouldn’t be affected.)
Changes in Mozilla’s security sandbox broke VA-API (the acceleration framework) integration.
Mozilla report: https://bugzilla.mozilla.org/show_bug.cgi?id=1751363
Mozilla report: 1751709 - RDD VA-API sandbox crashes due to denied getpwuid_r access
Fedora bugs, closed in favor of the upstream bugs:
Bugzilla report: 2063564 – Video players crashing in Firefox
Bugzilla report: 2063408 – ff-98.0 broke video playback