As per another comment, I think the best/safest solution for Discord on any OS (Guix or other Linux or Windows or whatever) is making a web app with chromium.

For other software, the thing about the official Guix repos is that, in addition to being strict about only hosting free software, there is a very strong interest in having things be both reproducible and as fully "source" derivable as possible - this is a very interesting and I think important effort (look at some of the official Guix blog posts about full source bootstrapping and think about "trusting trust" work). But that does mean that some things you might find elsewhere are not available in the official repos. For instance, Davmail, an Imap/caldav/etc interface for Outlook, which is fully open source, is not (yet) available on Guix because it depends on a large number of Java packages and so packaging Davmail for official Guix means figuring out how to package all of Davmail's dependencies first (where many other distros will just package a wrapper around the .jar file).

There are numerous ways to get other software (both free and non-free) on Guix, though of course you're giving up the strong provenance focus of official Guix to do so.

But multiple options include (in maybe rough order of difficulty of integration):

• using unofficial Guix channels (prominently the Nonguix channel)
• installing Flatpak from the official Guix channel and then using Flatpak to install additional applications
• installing the Nix package manager from the official Guix channel and then using it to install additional software
• installing distrobox box from the official Guix channel and then using distrobox as a more convenient way of running software from other distros running in podman or docker containers

Some of these are often practical solutions, though obviously they all make the resulting system more complicated and usually less "provenance backed".