Can't add a printer in Catalina
Following problem described here https://discussions.apple.com/thread/8099770
I cannot add printer anymore. After I have selected printer and driver and click on the "Add" button the window closes and nothing happens. No printer is added to the list.
The solution is : in /private/etc/cups/ folder there should be a /ppd folder which in my case was an alias with the same name. Thus creating ppd folder I was able to add printer normally.
Hope that helps