I now have installed scangearmp-common and scangearmp-mp520
Both are shown in yast when searching them under new software installation.
In GIMP it is shown as ScanGear MP… - but when klicking on it nothing happens.
The konsole shows following:
linux-amq9:/home/wsra # scangearmp
Cannot find Canon MFP scanner device.
linux-amq9:/home/wsra # sane-find-scanner
found USB scanner (vendor=0x04a9 [Canon], product=0x1724 [MP520 series]) at libusb:001:002
linux-amq9:/home/wsra # scanimage -L
No scanners were identified.