Oh, and to replace the same character string in a bunch of filenames or dirnames, (e.g. in our case replace the mac address in all dirnames by another mac address), one can do:
for dirname in $(find /home/defaultuser/.local/share/system/privileged/connman/wifi* -type d) ;do mv $dirname $(echo $dirname | sed -e s/xxxxxxxxxxxx/yyyyyyyyyyyy/);done
where xxxxxxxxxxxx is the initial mac address and yyyyyyyyyyyy is the new mac address.