tl/dr: Because of what I read in the wiki, I tried to manually set up graphics drivers to get hardware acceleration, failed, and realized after a reinstall that it works out of the box.

This doesn’t sound like a problem and it isn’t.
But I just spent the better part of a day trying to get jitter-free video to work in Firefox and failed. Because of these entries in the wiki:

https://wiki.archlinux.org/title/Xorg#Driver_installation

The Linux kernel includes open-source video drivers and support for hardware accelerated framebuffers. However, userland support is required for OpenGL and 2D acceleration in X11.
In order for video acceleration to work, and often to expose all the modes that the GPU can set, a proper video driver is required
For Intel graphics on 4th generation and above, see Intel graphics#Installation for available drivers.

So I headed over to https://wiki.archlinux.org/title/Intel_graphics#Installation and started installing driver packages, VAAPI tools, etc… I’m sure I must have done something wrong here, cause I still couldn’t get jitter-free video in Firefox. And then I started doing stuff I found with google searches. And reinstalled twice and went through the entire process again…
In the end, I could verify that hardware acceleration actually worked on my system and was used by Firefox. But video playback was still incredibly choppy. I checked that my internet speed isn’t the problem, it was definitely something related to video decoding, since every time it jittered, CPU usage spiked.

I was about ready to give up and try it on Ubuntu, but I couldn’t bring myself to do it.

I tried one last time, reinstalled Arch and just started the video streaming site without doing anything at all to set up graphics (except enabling Wayland for Firefox). And the video runs fine! Hardware-acceleration in Firefox works, too. And I’m stumped as to why, cause my understanding from the wiki articles was that you need to set it up first.

Any ideas what I did or read wrong in the beginning? Is it because I’m not using Xorg for Firefox? Or because this is only necessary with a dedicated GPU?