I followed the Configuration via LuCI section of the Wi-Fi Extender/Repeater with Bridged AP over Ethernet guide.
It's working as expected. I can get to the internet when connecting to the bridged AP with WiFi, and a LAN device connected to the switch also gets internet.
I'd like to set a static IP for the device connected to the dumb AP, though, since I'd like to forward ports to that device. I can see the device's IP address in Status > Routing, and I can see its hostname in the Active DHCPv6 Leases section of the status overview page, but I don't see any such entry in DHCPv4.
Maybe I could do this with SSH, but I'm wondering if not seeing this device is a symptom of some other misconfiguration I should fix.