In web browsers, things are more delicate because videos live within the complex context that is a webpage -with its own layer of hardware acceleration!-, and failures can be brutal depending on your browser, hardware and driver quality (crashes, video corruption, etc).
The pain-in-the-ass-ness to enable it on a given browser varies with time and browser/OS and along regressions, stack changes, and maintainer priorities. From personal experience during the past years, it has never been great on Linux:
- In Firefox, regressions have been frequent.
- In Chrome, the feature is here but Google disables it at build time in their official builds (my personal intuition is that they do enable it for their Chromebooks, but they don't want to support the wild west of broader Linux configuration and old/broken driver fun). However, out of official Chrome builds, several distributions builds (Arch, Debian) of Chromium now enable it at build time, so it's possible to try to use it.
So, it's finnicky to enable, but sometimes feasible, until it's no longer :D . To give it a try on a Linux box, the well-maintained Arch wiki is what you want (and these sections are mostly not specific to Arch):
- Firefox: https://wiki.archlinux.org/title/Firefox#Hardware_video_acce...
- Chrome: https://wiki.archlinux.org/title/Chromium#Hardware_video_acc...