EDIT

  @btx

Same problem with R605, there should be generic form to make DDNS as you wish.

For affraid it is simpler because now you can use simple link.

Considering direct competitior ubiquiti edgerouter x, it has no typical functionality because DDNS refresh is done without scheduler only when ip changes.

So if you want to do it periodically you need use cli to create task. That is advantage of filesystem access for users.

Here with tp-link routers you can do nothing, you have somekind of ssh access but not configurable at all.

Looking at specification new tp-link vpn routers are less powerfull that old good edgerouterx, tp-link also has only substitute of filesystem that er-x has.

Maybe this explains why it is so dificult for tp-link to implement requested functionalites - they need add extra effort to pack it into such shrinked device.

EDIT