Launcher always exits with "ERROR: Config name must not contain upper case characters, spaces or special characters."

Did you also export LANG=en_US.utf8 before running it? The current shell could have it’s own independent idea of locale.

As a separate matter, the test could be rewritten to be less locale sensitive:

#!/bin/bash
re='[^abcdefghijklmnopqrstuvwxyz0123456789_.-]'
if [[  $1 =~ $re ]];
  then
      echo "ERROR: Config name must not contain upper case characters, spaces or special characters. Correct config name and rerun $0."
fi

But maybe people wanted [configname] to work…