Some media packages need to access /dev/video and other related device nodes during build. This often causes a sandbox violation and requires ebuild maintainers to add exceptions for those devices.
As drobbins stated in FL-9287, "What would be even better is to have a chroot set up for building that only contains critical device nodes necessary, and not hardware-specific device nodes. If portage used this, we wouldn't need to mask out hardware devices on user's systems."
and later (to me) in Discord: "there is too much exposure of the local environment and devices to the build process in portage ".
This would resolve FL-6926