Re: 'systemctl stop cups'...

Simple and straight forward answer:  No.
It is very obvious that in my case both AiO-printers had been detected via CUPS only.


user@user-ThinkPad-T60p:~$ systemctl start cups
user@user-ThinkPad-T60p:~$ hp-scan

  Num       Scan device URI                                     
  --------  ----------------------------------------------------
  0         hpaio:/net/Officejet_Pro_8500_A910?ip=192.168.178.24
  1         hpaio:/net/HP_OfficeJet_Pro_8730?ip=192.168.178.40  


user@user-ThinkPad-T60p:~$ systemctl stop cups
user@user-ThinkPad-T60p:~$ hp-scan
error: No device selected/specified or that supports this functionality.

Apr 25 20:41:06 user-ThinkPad-T60p python[18067]: io/hpmud/model.c 532: no icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/models.dat
Apr 25 20:41:06 user-ThinkPad-T60p python[18067]: io/hpmud/model.c 543: no icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/unreleased/unreleased.dat
Apr 25 20:41:06 user-ThinkPad-T60p python[18067]: io/hpmud/model.c 532: no hp_icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/models.dat
Apr 25 20:41:06 user-ThinkPad-T60p python[18067]: io/hpmud/model.c 543: no hp_icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/unreleased/unreleased.dat
Apr 25 20:41:11 user-ThinkPad-T60p hp-scan[18067]: hp-scan[18067]: error: No device selected/specified or that supports this functionality.

---------------------------------------------------------------------------------------

Did some more testing, as my 8730 had a few unnessessary protocols disabled.

In fact, it is NOT AirPlay, which makes the difference.  It is Bonjour alone.
With Bonjour ON and AirPlay OFF on the 8730 and CUPS still stopped I get this:

Apr 25 20:59:30 user-ThinkPad-T60p hp-scan[18208]: hp-scan[18208]: warning: No destinations specified. Adding 'file' destination by default.
Apr 25 20:59:32 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/model.c 532: no icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/models.dat
Apr 25 20:59:32 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/model.c 543: no icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/unreleased/unreleased.dat
Apr 25 20:59:32 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/model.c 532: no hp_icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/models.dat
Apr 25 20:59:32 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/model.c 543: no hp_icejet_pro_8500_a910 attributes found in /usr/share/hplip/data/models/unreleased/unreleased.dat
Apr 25 20:59:32 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/model.c 532: no officejet_pro_8730 attributes found in /usr/share/hplip/data/models/models.dat
Apr 25 20:59:32 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/model.c 543: no officejet_pro_8730 attributes found in /usr/share/hplip/data/models/unreleased/unreleased.dat
Apr 25 20:59:37 user-ThinkPad-T60p hp-scan[18208]: hp-scan[18208]: warning: File destination enabled with no output file specified.
Apr 25 20:59:37 user-ThinkPad-T60p hp-scan[18208]: hp-scan[18208]: warning: Defaulting to '/home/user/hpscan010.png'.
Apr 25 20:59:38 user-ThinkPad-T60p hp-scan[18208]: hp-scan[18208]: error: No data read.
Apr 25 20:59:38 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/hpmud.c 373: device_cleanup: device uri=hp:/net/hp_officejet_pro_8730?ip=192.168.178.40&queue=false
Apr 25 20:59:38 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/hpmud.c 385: device_cleanup: close device dd=1...
Apr 25 20:59:38 user-ThinkPad-T60p hp-scan[18208]: io/hpmud/hpmud.c 387: device_cleanup: done closing device dd=1

Now, the 8730 has the same 3-letters-lost issue as expected.  But somehow the uri is still deduced.