I finally managed to get my DynDNS to work with ddclient
checkip -t 1/0 did not provide any reply. Removing it completely worked
# /usr/local/opnsense/scripts/ddclient/checkip -i re0 -s dyndns
xxx.xxx.xxx.xxx
checkip -t 1/0 did not provide any reply. Removing it completely worked
# /usr/local/opnsense/scripts/ddclient/checkip -i re0 -s dyndns
xxx.xxx.xxx.xxx