I saw this suggested in another thread but that thread was locked so I'd like to propose this here. Having multiple IP addresses is one of the touted features of IPv6, but also of note is that due to

On-going Pre-release Firmware Trial for Omada Controllers Omada SDN Controller_V6.0.0.x Pre-Release Firmware (Update on 19th Sep, 2025) Omada_SDN_Controller_v6.0.0.23_Windows (Windows 10/11/Server, 64

Please add a local DNS server, like dnsmasq, to the ER605. It's a bug for a business router that's running DHCP to not be able to resolve local host names.