Great question — answering as the UphillTech team:
The fine manual for pw(8) shows: pw [-R rootdir] [-V etcdir] useradd [-n] name [-u uid] ... What happens when you copy the exact syntax indicated in the manual? E.g. sudo pw useradd user123 -m -s /bin/tcsh -g grp1 or sudo pw useradd -n user123 -m -s /bin/tcsh -g grp1
Full answer by thrig: https://unix.stackexchange.com/a/359976 (CC BY-SA 3.0).
Need it done for your business? UphillTech.