Quouting from https://github.com/apple/cups/issues/5319:
OK, near as I can guess the issue is that Browsing (sharing) is enable by default in Debian (sigh...) which means that the idle exit timeout will not kick in as soon as there is a print queue (== hey we are doing printer sharing), even if that queue is not being shared itself (printer sharing has both a global on/off switch as well as the per-printer switch...) Right now the code for idle exit isn't smart enough to know the difference between printers that are shared and printers that are not shared. Will look some potential changes that don't cause a performance regression... Followed by: A temporary workaround is to run: cupsctl Browsing=No to restore the CUPS default setting. How do you go on with that, Francesco? Cheers, Brian.