So Mojave had an update today - 10.14.5. With fear and trepidation, I installed the update not knowing if my ScanSnap S1500M would be bricked (Manager ver. 6.3 L70). But I am pleased to report that it continues to scan like its old self. Hallelujah! At least until the next macOS update . . .
@JaxGirl - thank you for the timely post. I’m in the same situation with the ScanSnap S1500M. I’ll consider this my clearance to update to Mojave 10.14.5.
Apparently the next major macOS (10.15) will be the last nail in the coffin for the S1500M and ScanSnap Manager. Big decision then - running VueScan or ExactScan software with the ScanSnap S1500M vs buying a new (non-Fujitsu) scanner.