I can confirm that smbspool is the problem. I unpacked the copy of smbspool from the older package smbclient-3.0.21b-1ubuntu1, and replaced /usr/bin/smbspool. Reverting to the older version of smbspool cures the problem.
So this bug should be labelled as belonging to package smbclient. (But unlike bugzilla, this launchpad doesn't seem to have a way for me to change the package.)
I can confirm that smbspool is the problem. I unpacked the copy of smbspool from the older package smbclient- 3.0.21b- 1ubuntu1, and replaced /usr/bin/smbspool. Reverting to the older version of smbspool cures the problem.
So this bug should be labelled as belonging to package smbclient. (But unlike bugzilla, this launchpad doesn't seem to have a way for me to change the package.)