I have a USB-connected HP DeskJet Ink Advantage 1515 printer/scanner. On my own system (this is a full Guix System, not Guix on a foreign distro) I modified the configuration.scm:
```scheme (use-package-modules #;... scanner) (operating-system #;... (services (append #;... (modify-services %desktop-services (sane-service-type _ => sane-backends)))) #;...) ``` After `sudo guix system reconfigure configuration.scm`, `simple-scan` still could not find it. However, on reboot, it was able to find my already-connected USB printer/scanner without any issues. Perhaps only some kind of force-trigger of `udev` would be needed after the above setup, but `udev` is pretty early in the Shepherd tree. On the other hand the `sane-service-type` documentation in `info guix` is ***severely*** lacking, and the documentation is somehow lost in the middle of documentation about geolocation services, so it should probably be fixed. Thanks raid5atemyhomework