After viewingthis thread from 2017, I am curious to know, is the clientsettings.cfg file still only supported for Windows and macOS? Maybe @AlanM knows.
I confirm that the clientsettings.cfg only works for Windows and Mac computers. Unix BES Clients use the file /var/opt/BESClient/besclient.config to store the agent settings and you can modify it so it contains the desired settings at install time.
Thank you very much for the update.