Nitpick: Browsers on Linux have been using hardware video display acceleration since the Netscape 0.9 / Mosaic days, but video codec acceleration has been spotty.
I have a GTX 1080 which performs wonderfully under Linux (Ubuntu) but I still have to go into Firefox and Chrome browser flags to force hardware accelerated GPU rendering on. Once that's enabled they work as well as Windows. New users may benefit if browsers prompted users to try forcing hardware acceleration and have the ability to easily disable it, or do so automatically if it detects crashes, e.g. where location, microphone and video settings can be toggled.
Which is why macOS, Windows and ChromeOS are the platforms for anyone who care about video hardware acceleration without messing with configurations.
ChromeOS is Linux.
I mean, sure, at a kernel level. It has its own GUI rendering stack (Freon) rather than the usual X11/Wayland of "normal" Linux, and it's Freon that has their acceleration support.
Not really, it is an implementation detail not exposed to users.
Even Crostini relies on containers and virtualization to expose a second kernel, WSL2 style.