Looking at the version of cups in Impish it seems that this change has made it into cups, subsequently I'm setting the bug to fix released.
** Changed in: cups (Ubuntu) Status: New => Fix Released -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1890572 Title: USB backend never ends if the printer is not connected To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cups/+bug/1890572/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs