> 
> Thank you for the hint - I didn't have udisks (or udisks2?) installed, so
> I have installed it, and now I get no desktop icon.
> But I can mount it from the cli, possibly because I have an fstab entry.
> But experiments are continuing...
> 

can you check if this somehow applies to you please?
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=650299