Thanks for the info, and sorry for the trouble. This isn't actually a foreign distro, my OS declaration just doesn't use %desktop-services, so the automatic setuid handling wasn't there. Thanks to your info I was able to manually add slock to setuid-programs and it's working fine from /run/setuid-programs now.
Sorry again about the bother, since this wasn't actually a guix problem, and thanks for the help!
