Unfunctional scanner in Ubuntu 20.10

As written to the sane-devel list, since upgrading to Ubuntu 20.10 yesterday my scanner refuses to scan. I'll write down what I have tried so far:

$ scanimage -L
No scanners were identified. If you were expecting something different,
check that the scanner is plugged in, turned on and detected by the
sane-find-scanner tool (if appropriate). Please read the documentation
which came with this software (README, FAQ, manpages).

Which is the base of the problem and this issue.

$ sane-find-scanner
 # sane-find-scanner will now attempt to detect your scanner. If the
 # result is different from what you expected, first make sure your
 # scanner is powered up and properly connected to your computer.

 # No SCSI scanners found. If you expected something different, make sure that
 # you have loaded a kernel SCSI driver for your SCSI adapter.

found USB scanner (vendor=0x04a9 [Canon], product=0x220d [CanoScan], chip=LM9832/3) at libusb:001:013
 # Your USB scanner was (probably) detected. It may or may not be supported by
 # SANE. Try scanimage -L and read the backend's manpage.

^^ So sane-find-scanner finds my scanner correctly as a libusb device

$ lsusb -v
Bus 001 Device 005: ID 04a9:220d Canon, Inc. CanoScan N670U/N676U/LiDE 20 
Device Descriptor:
 bLength                18
 bDescriptorType         1
 bcdUSB               1.10
 bDeviceClass          255 Vendor Specific Class
 bDeviceSubClass         0  
 bDeviceProtocol         0  
 bMaxPacketSize0         8
 idVendor           0x04a9 Canon, Inc.
 idProduct          0x220d CanoScan N670U/N676U/LiDE 20
 bcdDevice            1.00
 iManufacturer          64 Canon
 iProduct               77 CanoScan
 iSerial                 0  
 bNumConfigurations      1
 Configuration Descriptor:
   bLength                 9
   bDescriptorType         2
   wTotalLength       0x0027
   bNumInterfaces          1
   bConfigurationValue     1
   iConfiguration          0  
   bmAttributes         0xa0
     (Bus Powered)
     Remote Wakeup
   MaxPower              500mA
   Interface Descriptor:
     bLength                 9
     bDescriptorType         4
     bInterfaceNumber        0
     bAlternateSetting       0
     bNumEndpoints           3
     bInterfaceClass       255 Vendor Specific Class
     bInterfaceSubClass      0  
     bInterfaceProtocol    255  
     iInterface              0  
     Endpoint Descriptor:
       bLength                 7
       bDescriptorType         5
       bEndpointAddress     0x81  EP 1 IN
       bmAttributes            3
         Transfer Type            Interrupt
         Synch Type               None
         Usage Type               Data
       wMaxPacketSize     0x0001  1x 1 bytes
       bInterval              16
     Endpoint Descriptor:
       bLength                 7
       bDescriptorType         5
       bEndpointAddress     0x82  EP 2 IN
       bmAttributes            2
         Transfer Type            Bulk
         Synch Type               None
         Usage Type               Data
       wMaxPacketSize     0x0040  1x 64 bytes
       bInterval               0
     Endpoint Descriptor:
       bLength                 7
       bDescriptorType         5
       bEndpointAddress     0x03  EP 3 OUT
       bmAttributes            2
         Transfer Type            Bulk
         Synch Type               None
         Usage Type               Data
       wMaxPacketSize     0x0040  1x 64 bytes
       bInterval               0
can't get debug descriptor: Resource temporarily unavailable
Device Status:     0x0000
 (Bus Powered)

$ dmesg -w
[ 1027.863405] usb 1-1: new full-speed USB device number 6 using xhci_hcd
[ 1028.023470] usb 1-1: New USB device found, idVendor=04a9, idProduct=220d, bcdDevice= 1.00
[ 1028.023475] usb 1-1: New USB device strings: Mfr=64, Product=77, SerialNumber=0
[ 1028.023479] usb 1-1: Product: CanoScan
[ 1028.023481] usb 1-1: Manufacturer: Canon

# scanimage -L (as root) no success

libsane in Ubuntu 20.10 is at 1.0.31-2

I'm running a self-compiled kernel 5.8.14, but the distro kernel 5.8.0 doesn't work as well.

I have succesfully scanned a week ago on this same hardware using Ubuntu 20.04, kernel 5.8.12

plustek is mentioned uncommented in /etc/sane.d/dll.conf

I'm a developer, so willing (and able) to compile test code to debug where in the chain (libusb?) things go wrong.