I think it would be nice to change the namecheapdns component to support multiple domains. This would be a breaking change, since the config would change from a single value to a list of values.
I created a workaround using a script and the RESTful Command integration. I update a number of subdomains using a script/s. It uses the DNS IP integration to fetch the public IP and to pass it to the RESTful command. Simply update the variables to fit your own environment.
/config/rest_command.yaml
namecheap_ddns:
url: "{{ namecheap_ddns_url }}"
method: get
verify_ssl: false
Sorry to bring this thread back, but if you are still using this integration, is it still working for you?
I just tried to set it up today, but putting the host as a wildcard gives a Updating namecheap domain failed error upon restarting home assistant.