Flashing seems not possible
I fixed the libusbx error
libusbx: error [op_set_interface] setintf failed error -1 errno 71 by following these instructions:

 echo "blacklist cdc_acm" &gt;/etc/modprobe.d/cdc_acm-blacklist.conf
 rmmod cdc_acm # ignore ERROR is not currently loaded


After that the "Setting up interface..." step passed well for me.