How to report/complain about non-crash usability problems?

[Tom Bertalan]

I just wanted to register a criticism of the new printer selection UI in 
the 18.04 settings app--on large networks, it shows a useless, 
ever-changing swarm of FREDS-MACBOOK-PRO shared printers, with no 
obvious way to even add a printer directly by address, and with existing 
installed printers mixed in with the macbooks.

However, this isn't a crash, which seems to be the main use-case 
considered by the Launchpad system. Maybe a mailing list?

Tom