Allow to add new printers via Printer Applications
New architecture of CUPS which will heavily rely on IPP does not use drivers but Printer Applications. These are mainly for printers which do not support newer IPP themselves. The printer Applications will add them the functionality of IPP service so that they can work in applications which rely on discoverability of printers via DNS-SD.
The new printer dialog needs to change in the way that it installs Printer Application for the printer selected by user. The Printer Application will make it available to the rest of the system.
This is a feature which will need a close collaboration with packaging system as we need to install correct Printer Application if it is not already installed. The probable tool for this will be PackageKit as it is already used for installing drivers right now.
One of the ways how to find which Printer Application to use will be via web service, see https://openprinting.github.io/OpenPrinting-News-November-2021/#printer-querying-on-the-openprinting-web-server for details.
This will be the only way for installing old printers since CUPS 3. Modern printers will be automatically available as IPP services via DNS-SD.
We also need to decide fomr which version of CUPS to switch to this new model as the Printer Applications will be available sooner then in the CUPS 3.