I, too, would like to see additional DDNS options available.  I personally use DuckDNS-org.

A custom DDNS option would be great, where the gateway can be configured to GET/POST to a URL 

Heres what I would envision custom DNS input screen to look like:

Service: [Custom DNS]

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Method: [GET/POST]

URL: [https://some-dns-com/update_ip?ip={ipaddress}&token=abcdef01234567890abcdef0123456789]

(Note use "{ipaddress}" to send current ip address)

Frequency: [Hourly/Daily]

Send request when WAN interface restores: [  ] Yes

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Note that most of the Custom DDNS websites allow for auto detection of WAN IP by getting the incoming IP address during the ip address update, or you can specify directly.

There's another suggestion with more votes for arbitrary DDNS services that you should probably go vote for.