It runs it in Debian-based KVM VMs, and it uses virtio-wayland[1] to pass the applications through to the host compositor, making them feel as if they are not running in a VM.
This architecture means that ChromeOS can preserve its readonly system partition, delta updates, and fast boot times while being able to run any Linux app. Very similar to Qubes, actually.
"Camera not supported yet" .. feature!
Write the support yourself! Publish it under the GPL! Share and enjoy! ;)
Of course, it can and hopefully will be improved by improvements to desktop Linux. I haven't kept up, but ChromeOS will probably be able to adopt newer open source desktop technologies like Wayland and Pipewire/XDG portals in order to get a better Linux multimedia experience, if they care to.