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: 1751363 - VA-API: creating video snapshot fails due to RDD sandbox + Since bug 1724385 (98), VAAPI fails in general due to RDD sandbox
Mozilla report: 1751709 - RDD VA-API sandbox crashes due to denied getpwuid_r access
Disable video hardware acceleration by opening
about:config page in Firefox and set
false (the default value). You’ll not have video acceleration, but the browser will function properly.
Alternatively, you can make the acceleration work by disabling the security sandbox, if you set the
MOZ_DISABLE_RDD_SANDBOX=1 environment variable. Please note that this is not recommended, because it makes your browser and your system more vulnerable to web attacks.