I got the solution! I filed a ticket with TP-Link support, and they gave me the answer. As it turns out, the Link-local Address must be the address of the client, not the router! So once I calculated...

@Clive_A, I am clearly using standalone mode, there is no controller. I have shown screenshots demonstrating that there is a prefix delegation server, and explained that the only possible purpose of...

Clive_A wrote If you use the Omada gear as the only PD in your IPv6 network, then the LAN config should be SLAAC+Stateless DHCP mode. If you need it to work, you set it to Get from Prefix Delegation...

Since we seem to be unable to communicate clearly, I am including screenshots to explain precisely what I am trying to understand. Here is my WAN configuration page (censored): As you can see, I am...

Let me bring this back to focus. Here are specific questions. What is the purpose of the Prefix Delegation Server? It is a separate configuration from the LAN configuration. The LAN handles IPv6...

How could that possibly be true? If subnetting was not intented to be supported, then the Prefix Delegation Server configuration would only allow a single entry for specifying a delegated prefix. But...