The DS Nix installer is close to becoming a first-class citizen for installing nix packages on non-NixOS distributions. One current issue though is that .desktop files for GUI apps are not auto-picked-up by the DE. This is easy to rectify though. Simply add a file to etc/profile.d/ containing the following line:

export XDG_DATA_DIRS="${HOME}/.nix-profile/share:/nix/var/nix/profiles/default/share:${XDG_DATA_DIRS}"

I called my file nix-xdg-data-dirs.sh but /etc/profile.d/ already contains nix.sh which calls /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh so the XDG_DATA_DIRS line could simply be added to this latter file by the installer.

Using the syntax of the existing file nix-daemon.sh, I believe the correct line to add to it would be:

export XDG_DATA_DIRS="$NIX_LINK/share:/nix/var/nix/profiles/default/share:$XDG_DATA_DIRS"

This could go directly after the existing export PATH command.
Many thanks for the great ongoing work!