I just browsed the pclinuxos forum, and seems someone else had an issue with synaptic. So, the following was suggested for upgrading/reinstalling (run as root):

I'm guessing it won't work. But, seems worth a try.

If you have a second computer then boot up your OS from it in a virtual machine. Get and copy the libraries you're missing over just enough so that rpm is working. Once rpm starts working you can begin to repair the system.

As mark_alfred suggests, use "ldd /usr/bin/rpm" to check and see what libraries you're missing.

See troubleshooting guides for "rpm repair linux" when you're web searching. e.g.

https://www.suse.com/communities/blo...on-and-repair/

Depending on your level of effort you should probably just reinstall. Make use of ansible to autoconfigure everything next time.