There seems to be a vital step missing in the following documentation:
That missing step would seem to be bridging the wireless network with an Ethernet adapter. Without that, I fail to see how this is going to work. But then of course I am looking at it from the perspective of my hardware (GL-AR150). That said, the "command line" version of the "Dumb AP" configuration does mention the bridging, but it's not mentioned in the LUCI configuration, nor in the "Bridged AP" procedure at all. Here's how it looks in LUCI for my device.
I'm happy to submit changes to add this, but before doing so I wanted to try to get some verification that, as a newbie, I've not missed something.