HP LaserJet Pro MFP M28a: unable to reach the scanner from XSane under Debian 11 using HPLIP

My OS is Debian 11 and my printer is an HP LaserJet Pro MFP M28a. After the first install using the hplip package, both printing and scanning were working fine but, for some reason, I had to reinstall the printer and then the scanner became unreachable from XSane at all. I have tried several options and I either get error message code 9 ("error: SANE: Error during device I/O") or 10 ("error: SANE: Out of memory (code=10)") when trying to launch XSane. Is it actually an error from XSane or from the whole configuration on my computer? By the way, here is the output from hp-check:

-check: info: :
hp-check: info: :[01mHP Linux Imaging and Printing System (ver. 3.21.2)[0m
hp-check: info: :[01mDependency/Version Check Utility ver. 15.1[0m
hp-check: info: :
hp-check: info: :Copyright (c) 2001-18 HP Development Company, LP
hp-check: info: :This software comes with ABSOLUTELY NO WARRANTY.
hp-check: info: :This is free software, and you are welcome to distribute it
hp-check: info: :under certain conditions. See COPYING file for more details.
hp-check: info: :
hp-check: info: :[01mNote: hp-check can be run in three modes:[0m
hp-check: info: :1. Compile-time check mode (-c or --compile): Use this mode before compiling the HPLIP supplied tarball (.tar.gz or .run) to determine if the
hp-check: info: :proper dependencies are installed to successfully compile HPLIP.
hp-check: info: :2. Run-time check mode (-r or --run): Use this mode to determine if a distro supplied package (.deb, .rpm, etc) or an already built HPLIP
hp-check: info: :supplied tarball has the proper dependencies installed to successfully run.
hp-check: info: :3. Both compile- and run-time check mode (-b or --both) (Default): This mode will check both of the above cases (both compile- and run-time
hp-check: info: :dependencies).
hp-check: info: :
hp-check: info: :Check types:
hp-check: info: :a. EXTERNALDEP - External Dependencies
hp-check: info: :b. GENERALDEP - General Dependencies (required both at compile and run time)
hp-check: info: :c. COMPILEDEP - Compile time Dependencies
hp-check: info: :d. [All are run-time checks]
hp-check: info: :PYEXT SCANCONF QUEUES PERMISSION
hp-check: info: :
hp-check: info: :Status Types:
hp-check: info: : OK
hp-check: info: : MISSING - Missing Dependency or Permission or Plug-in
hp-check: info: : INCOMPAT - Incompatible dependency-version or Plugin-version
hp-check: info: :
warning: [01mdebian-11 version is not supported. Using debian-10.7 versions dependencies to verify and install...[0m
hp-check: info: :
hp-check: info: :---------------
hp-check: info: :| SYSTEM INFO |
hp-check: info: :---------------
hp-check: info: :
hp-check: info: : Kernel: 5.10.0-8-amd64 #1 SMP Debian 5.10.46-4 (2021-08-03) GNU/Linux
 Host: Aragorn
 Proc: 5.10.0-8-amd64 #1 SMP Debian 5.10.46-4 (2021-08-03) GNU/Linux
 Distribution: debian 11
hp-check: info: : Bitness: 64 bit

hp-check: info: :
hp-check: info: :-----------------------
hp-check: info: :| HPLIP CONFIGURATION |
hp-check: info: :-----------------------
hp-check: info: :
hp-check: info: :HPLIP-Version: HPLIP 3.21.2
hp-check: info: :HPLIP-Home: /usr/share/hplip
warning: HPLIP-Installation: Auto installation is not supported for debian distro 11 version
hp-check: info: :
hp-check: info: :[01mCurrent contents of '/etc/hp/hplip.conf' file:[0m
hp-check: info: :# hplip.conf. Generated from hplip.conf.in by configure.

[hplip]
version=3.21.2

[dirs]
home=/usr/share/hplip
run=/var/run
ppd=/usr/share/ppd/hplip/HP
ppdbase=/usr/share/ppd/hplip
doc=/usr/share/doc/hplip
html=/usr/share/doc/hplip-doc
icon=no
cupsbackend=/usr/lib/cups/backend
cupsfilter=/usr/lib/cups/filter
drv=/usr/share/cups/drv
bin=/usr/bin
apparmor=/etc/apparmor.d
# Following values are determined at configure time and cannot be changed.
[configure]
network-build=yes
libusb01-build=no
pp-build=no
gui-build=yes
scanner-build=yes
fax-build=yes
dbus-build=yes
cups11-build=no
doc-build=yes
shadow-build=no
hpijs-install=yes
foomatic-drv-install=yes
foomatic-ppd-install=no
foomatic-rip-hplip-install=no
hpcups-install=yes
cups-drv-install=yes
cups-ppd-install=no
internal-tag=3.21.2
restricted-build=no
ui-toolkit=qt5
qt3=no
qt4=no
qt5=yes
policy-kit=yes
lite-build=no
udev_sysfs_rules=no
hpcups-only-build=no
hpijs-only-build=no
apparmor_build=no
class-driver=no

hp-check: info: :
hp-check: info: :[01mCurrent contents of '/var/lib/hp/hplip.state' file:[0m
hp-check: info: :[plugin]
installed = 1
eula = 1
version = 3.21.2

hp-check: info: :
hp-check: info: :[01mCurrent contents of '~/.hplip/hplip.conf' file:[0m
hp-check: info: :[commands]
scan = /usr/bin/xsane -V %SANE_URI%

[fax]
email_address =
voice_phone =

[installation]
date_time = 08/16/21 17:03:40
version = 3.21.2

[last_used]
device_uri = escl:http://127.0.0.1:60001 
printer_name = Imprimante
working_dir = .

[polling]
device_list =
enable = false
interval = 5

[refresh]
enable = true
rate = 30
type = 1

[settings]
systray_messages = 0
systray_visible = 1

[upgrade]
last_upgraded_time = 1607445828
notify_upgrade = true
pending_upgrade_time = 0

hp-check: info: :       
hp-check: info: :
hp-check: info: :-------------------------
hp-check: info: :| External Dependencies |
hp-check: info: :-------------------------
hp-check: info: :
hp-check: info: :[31;01m error: cups CUPS - Common Unix Printing System REQUIRED 1.1 - INCOMPAT 'CUPS may not be installed or not running'[0m
hp-check: info: : gs GhostScript - PostScript and PDF language interpreter and previewer REQUIRED 7.05 9.53.3 OK -
hp-check: info: : xsane xsane - Graphical scanner frontend for SANE OPTIONAL 0.9 0.999 OK -
hp-check: info: : scanimage scanimage - Shell scanning program OPTIONAL 1.0 1.0.31 OK -
hp-check: info: : dbus DBus - Message bus system REQUIRED - 1.12.20 OK -
hp-check: info: : policykit PolicyKit - Administrative policy framework OPTIONAL - 0.105 OK -
hp-check: info: : network network -wget OPTIONAL - 1.21 OK -
hp-check: info: : avahi-utils avahi-utils OPTIONAL - 0.8 OK -
hp-check: info: :
hp-check: info: :------------------------
hp-check: info: :| General Dependencies |
hp-check: info: :------------------------
hp-check: info: :
hp-check: info: : libjpeg libjpeg - JPEG library REQUIRED - - OK -
hp-check: info: : cups-devel CUPS devel- Common Unix Printing System development files REQUIRED - - OK -
hp-check: info: : cups-image CUPS image - CUPS image development files REQUIRED - - OK -
hp-check: info: : libpthread libpthread - POSIX threads library REQUIRED - b'2.31' OK -
hp-check: info: : libusb libusb - USB library REQUIRED - 1.0 OK -
hp-check: info: : sane SANE - Scanning library REQUIRED - - OK -
hp-check: info: : sane-devel SANE - Scanning library development files REQUIRED - - OK -
hp-check: info: : libavahi-dev libavahi-dev REQUIRED - - OK -
hp-check: info: : libnetsnmp-devel libnetsnmp-devel - SNMP networking library development files REQUIRED 5.0.9 5.9 OK -
hp-check: info: : libcrypto libcrypto - OpenSSL cryptographic library REQUIRED - 1.1.1 OK -
hp-check: info: : python3X Python 2.2 or greater - Python programming language REQUIRED 2.2 3.9.2 OK -
hp-check: info: : python3-notify2 Python libnotify - Python bindings for the libnotify Desktop notifications OPTIONAL - - OK -
hp-check: info: :[31;01m error: python3-pyqt4-dbus PyQt 4 DBus - DBus Support for PyQt4 OPTIONAL 4.0 - MISSING 'python3-pyqt4-dbus needs to be installed'[0m
hp-check: info: :[31;01m error: python3-pyqt4 PyQt 4- Qt interface for Python (for Qt version 4.x) REQUIRED 4.0 - MISSING 'python3-pyqt4 needs to be installed'[0m
hp-check: info: : python3-dbus Python DBus - Python bindings for DBus REQUIRED 0.80.0 1.2.16 OK -
hp-check: info: : python3-xml Python XML libraries REQUIRED - 2.2.10 OK -
hp-check: info: : python3-devel Python devel - Python development files REQUIRED 2.2 3.9.2 OK -
hp-check: info: : python3-pil PIL - Python Imaging Library (required for commandline scanning with hp-scan) OPTIONAL - 8.1.2 OK -
hp-check: info: : python3-reportlab Reportlab - PDF library for Python OPTIONAL 2.0 3.5.59 OK -
hp-check: info: :
hp-check: info: :--------------
hp-check: info: :| COMPILEDEP |
hp-check: info: :--------------
hp-check: info: :
hp-check: info: : libtool libtool - Library building support services REQUIRED - 2.4.6 OK -
hp-check: info: : gcc gcc - GNU Project C and C++ Compiler REQUIRED - 10.2.1 OK -
hp-check: info: : make make - GNU make utility to maintain groups of programs REQUIRED 3.0 4.3 OK -
hp-check: info: :
hp-check: info: :---------------------
hp-check: info: :| Python Extentions |
hp-check: info: :---------------------
hp-check: info: :
hp-check: info: : cupsext CUPS-Extension REQUIRED - 3.21.2 OK -
hp-check: info: : hpmudext IO-Extension REQUIRED - 3.21.2 OK -
hp-check: info: :
hp-check: info: :----------------------
hp-check: info: :| Scan Configuration |
hp-check: info: :----------------------
hp-check: info: :
hp-check: info: :'/etc/sane.d/dll.d/hpaio' not found.
hp-check: info: : hpaio HPLIP-SANE-Backend REQUIRED - 3.21.2 OK 'hpaio found in /etc/sane.d/dll.conf'
hp-check: info: : scanext Scan-SANE-Extension REQUIRED - 3.21.2 OK -
hp-check: info: :
hp-check: info: :------------------------------
hp-check: info: :| DISCOVERED SCANNER DEVICES |
hp-check: info: :------------------------------
hp-check: info: :
hp-check: info: :device `escl:http://127.0.0.1:60001 ' is a HP LaserJet MFP M28a (A7B2AA) (USB) flatbed scanner
device `hpaio:/usb/HP_LaserJet_MFP_M28-M31?serial=VNC3R77190' is a Hewlett-Packard HP_LaserJet_MFP_M28-M31 all-in-one
device `hpaio:/net/hp_laserjet_mfp_m28-m31?ip=127.0.0.1&queue=false' is a Hewlett-Packard hp_laserjet_mfp_m28-m31 all-in-one
device `escl:http://127.0.0.1:60001 ' is a HP LaserJet MFP M28a (A7B2AA) (USB) flatbed scanner
device `hpaio:/usb/HP_LaserJet_MFP_M28-M31?serial=VNC3R77190' is a Hewlett-Packard HP_LaserJet_MFP_M28-M31 all-in-one
device `hpaio:/net/hp_laserjet_mfp_m28-m31?ip=127.0.0.1&queue=false' is a Hewlett-Packard hp_laserjet_mfp_m28-m31 all-in-one

hp-check: info: :
hp-check: info: :--------------------------
hp-check: info: :| DISCOVERED USB DEVICES |
hp-check: info: :--------------------------
hp-check: info: :
hp-check: info: : Device URI Model
hp-check: info: : ------------------------------------------------- ----------------------------
hp-check: info: : hp:/usb/HP_LaserJet_MFP_M28-M31?serial=VNC3R77190 HP LaserJet MFP M28-M31
hp-check: info: :
hp-check: info: :---------------------------------
hp-check: info: :| INSTALLED CUPS PRINTER QUEUES |
hp-check: info: :---------------------------------
hp-check: info: :
hp-check: info: :
hp-check: info: :[01m[0m
hp-check: info: :[01m[0m
hp-check: info: :Type: Unknown
hp-check: info: :Device URI: implicitclass://HP_LaserJet_MFP_M28a_A7B2AA_USB_/
hp-check: info: :
hp-check: info: :[01m[0m
hp-check: info: :[01m[0m
hp-check: info: :Type: Printer
hp-check: info: :Device URI: hp:/usb/HP_LaserJet_MFP_M28-M31?serial=VNC3R77190
hp-check: info: :Communication status: Good
hp-check: info: :
hp-check: info: :
hp-check: info: :--------------
hp-check: info: :| PERMISSION |
hp-check: info: :--------------
hp-check: info: :
hp-check: info: :USB Imprimante Required - - OK Node:'/dev/bus/usb/001/006' Perm:' root lp rw- rw- rw- rw- rw- r--'
hp-check: info: :
hp-check: info: :-----------
hp-check: info: :| SUMMARY |
hp-check: info: :-----------
hp-check: info: :
hp-check: info: :[01mMissing Required Dependencies[0m
hp-check: info: :[01m-----------------------------[0m
error: 'cups' package is missing or 'cups' service is not running.
error: 'libcups2' package is missing/incompatible
error: 'python3-pyqt4' package is missing/incompatible
error: 'gtk2-engines-pixbuf' package is missing/incompatible
hp-check: info: :
hp-check: info: :[01mMissing Optional Dependencies[0m
hp-check: info: :[01m-----------------------------[0m
error: 'python3-dbus.mainloop.qt' package is missing/incompatible
hp-check: info: :
hp-check: info: :Total Errors: 3
hp-check: info: :Total Warnings: 0
hp-check: info: :
hp-check: info: :
hp-check: info: :Done.

I know there is some warning telling me Debian 11 is *not supported* and that some required packages are *missing* (and I did not remove them since then), but I **did manage** to make the scanner work at first, so there must be a way to get it back running (without messing too much with the packages).