CUPS printers are not selectable in the graphical interface

My Linux (RHEL8) has a strange problem with the printers: I have printers installed on CUPS, but they are not displayed in the programs on the graphical interface! When I try to print from a text editor or a browser, the only printer available is the Save PDF option. However, when I open http://localhost:631 , the printers are there. I can even print test pages successfully. I thought it was a desktop environment problem (I'm using Xfce4). However I logged in using Gnome, and the behavior is the same. Any ideas?

Question by moser on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.