I searched, but could not find a bug-category for
kcmshell5, let alone kcmshell5 kcm_users.

STEPS TO REPRODUCE
01. Open a terminal
02. Type: kcmshell5 kcm_users
03. On your computer's keyboard, press-n-release: Enter
04. In the window that opens, left-click the button labelled: Add New User
05. In the box labelled Name, type a person's name
06. In the box labelled Username, type a sensible user-name
07. In the drop-down list labelled Account, choose Standard
08. In the box labelled Password, type a password
09. In the box labelled Confirm password, type the same password used in step 8
10. Left-click the button labelled: Create
11. Open another terminal and type: ls -lh /home
12. On your computer's keyboard, press-n-release: Enter

Observe that no new user has been created using the User Management
module of kcmshell5, at least not in the /home directory.

OBSERVED RESULT
No new users are created using the module kcmshell5 kcm_users

EXPECTED RESULT
New users should be created using the module kcmshell5 kcm_users

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 5.14.14/5.23.1
(available in About System)
KDE Plasma Version: 5.23.1 
KDE Frameworks Version: 5.87.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
Aside from seeing that no user directory is created in /home for
users that are "created" in kcmshell5 kcm_users, one can also open
the Control Center (in my fave distro), click on "Manage users on
system", and see that no new user is created using the kcmshell5
kcm_users module.

I should very, very, very much genuinely appreciate it if you
kindly KDE/Plasma folks could pretty please with sugar on top
rip out the code for kcmshell5 kcm_users (the work of which
is already done [in the distro I use] quite nicely by userdrake)
and put the new code for a modern, highly polished, incredibly 
user-configurable and glitzy version of Desktop Cube and Flip
Switch back into KDE/Plasma.

None of the Bug IDs listed as Possible Duplicates (which appeared
below where I typed this bug report) [BugIDs: 337230, 342588, 382874,
384107, 411758, 432838] list the same problem as the one I'm 
reporting in above.
423221, 

Incalculably appreciatively,
Dean