@otini that’s correct on distros following FSDG†.
Outside of official Guix places we can do whatever we want including switching to upstream kernel Linux, installing firmware blobs, or even proprietary user apps. (There are already examples of those e.g. on Gitlab or Github).
Inside official Guix places there is no support for proprietary software.
†https://www.gnu.org/distros/free-system-distribution-guidelines.html.en