Checkbox  'Share the devices of this server' in the server UI -> Devices panel doesn't disable the sharing of devices. Steps to reproduce:

1) Open the UI -> Settings -> Server -> Devices panel
2) Uncheck option  'Share the devices of this server'
3) Close the UI and reopen it: option  'Share the devices of this server' is still checked.

As a workaround, instead of using the general option  'Share the devices of this server', disable each device one by one by unchecking items (Disks, Printers etc ...)

This problem can affect also versions previous than v8.5.