Here are the instructions to use GFS, Cosmic or the Pantheon repositories threw slackpkg+

====GFS====
1. Download and install slackpkg+ package from http://slakfinder.org/slackpkg+/
2. If you plan on using slackpkg+ you will need to set the PKGS_PRIORITY=( gfs ) 
   to gnome so that any packages in this repository do not get overwritten by Slackware's packages. 
   Granted there is only 1 to 3 packages that would get overwritten. Those packages would be: gjs, 
   gtk4,and pango or libsoup3 ( if it is included within the repositories .)
   (* You may remove other repositories (except slackpkgplus) if you don't use it  *)
3. Add gfs repository information and match it with your Slackware and 
   GFS version, and your architecture
   Example:

   For Slackware 15.0 (64 bit) and GNOME 41.10:
   MIRRORPLUS['gfs']=https://slackware.uk/people/n4t3r/gfs/15.0/41.10/x86_64/
   MIRRORPLUS['gfs']=https://reddoglinux.ddns.net/linux/gnome/41.x/x86_64/

   For Slackware Current (64 bit) and GNOME 49:
   MIRRORPLUS['gfs']=https://slackware.uk/people/n4t3r/gfs/current/49/x86_64/
   MIRRORPLUS['gfs']=https://reddoglinux.ddns.net/linux/gnome/49.x/x86_64/

4. Run slackpkg update gpg && slackpkg update && slackpkg install gfs && slackpkg upgrade-all
5. You can start managing your GFS packages through slackpkg+

====Cosmic Desktop====
1. If you plan on using slackpkg+ you will need to set the PKGS_PRIORITY=( cosmic )
   to cosmic so that any packages in this repository do not get overwritten by Slackware's packages.
2. Add cosmic repository information and match it with your Slackware and
   Cosmic version, and your architecture
   Example:

   For Slackware Current (64 bit) and Cosmic Desktop 1.0.0.beta.1.1:
   MIRRORPLUS['cosmic']=https://slackware.uk/people/n4t3r/cosmic/x86_64
   MIRRORPLUS['cosmic']=https://reddoglinux.ddns.net/linux/cosmic/x86_64

3. Run slackpkg update gpg && slackpkg update && slackpkg install cosmic && slackpkg upgrade-all
4. You can start managing your Cosmic Desktop packages through slackpkg+

====Pantheon Desktop====
1. If you plan on using slackpkg+ you will need to set the PKGS_PRIORITY=( psb )
   to psb so that any packages in this repository do not get overwritten by Slackware's packages.
2. Add pantheon repository information and match it with your Slackware and
   Pantheon version, and your architecture
   Example:

   For Slackware Current (64 bit) and Pantheon Desktop 8.x:
   MIRRORPLUS['psb']=https://slackware.uk/people/n4t3r/pantheon/current-8
   MIRRORPLUS['psb']=https://reddoglinux.ddns.net/linux/pantheon/current-8

3. Run slackpkg update gpg && slackpkg update && slackpkg install psb && slackpkg upgrade-all
4. You can start managing your Pantheon Desktop packages through slackpkg+