I have added my Canon PIXMA printer by CUPS successfully and able to see it in various applications such as Chrome or Firefox. But unfortunately most other apps cannot show it, e.g. KWrite, Okular, Gwenview.
I tried to look for similar post in this forum but cannot find one.
Today I tried to make sure the print-manager and system-config-printer are update to date. pacman has found update available for upgraded package pugixml (1.13-1 → 1.14-1). After that and a system restart, all KDE apps able to show the network printers.
Not sure if that’s related, but it is working now.