Messages

Yes, this is due to the native backend setting configured on the General Settings Tab.

After changing this to ddclient, I still have issues with configuring it to work correctly with Namecheap.

I suspect this is the format that need to be used in the ddclient.conf file:
https://www.namecheap.com/support/knowledgebase/article.aspx/583/11/how-do-i-configure-ddclient/