Hello, Same problem for me as well as for other people at [1]. This happened after upgrading to 'buster' the machine where the scanner is plugged. Adding the udev rule fixes the issue. This regression is annoying, it would be nice for other users if our dear maintainers could fix it. :-)
Thanks & regards [1] https://www.raspberrypi.org/forums/viewtopic.php?t=243513 -- Florent
