Reporting good news instead of failure. Upgraded to Mojave (hard disk reformat, full reinstall to OS Version 10.14.4 without doing any prep work on Fujitsu software before hand. Without “upgrading” to home, i.e. using ScanSnap Manager Version 6.3 L70 … it just works.
So cancelling plans to move to a new scanner by a different manufacturer. Changing is probably inevitable, but for time being will leave well enough alone.