They needed to compile the kernel because they were using the full kernel. The main package repository (and thus the main binary caches) only include a de-blobb

They needed to compile the kernel because they were using the full kernel. The main package repository (and thus the main binary caches) only include a de-blobbed version of the kernel. To get standard Linux including all the blobs, you need to use the “nonguix” package repository. The nonguix folks do have a binary cache server, but using it during install is slightly annoying. I currently have a guix vm compiling Linux for exactly this reason. Since you likely won’t be installing much else from nonguix during system setup, you only need to compile the kernel and other bloby things you choose to include (e.g. firmware, microcode).