I have a Raspberry Pi 4B I use to display a Home Assistant dashboard, it includes cameras from around my house as well. After a fresh install of my RPI these camera streams don’t stream, until I install the below packages.

libgles2-mesa
libgles2-mesa-dev
xorg-dev

Video decoding seems to be enabled on Chromium by default now, but I also enable these flags which I found in an article here - although I’m relatively certain you no longer need to do this! I just haven’t gotten round to testing that.

ignore-gpu-blocklist
enable-gpu-rasterization