v1.28.9054 MIPSR2-beta K26 USB Ext
New hardware, just did a fresh install of build 54 and reset nvram. I enabled Web Admin local and remote access, but netstat shows (and confirmed with nmap from another host) that only the internal interface is listening. I tried toggling SSL, changing ports, etc, but the result was the same.
I tried resetting nvram and immediately enabling remote https access before changing any other settings, and the result was the same.
I have the mini of build 54 running on another router of the same model and remote access works fine there, so it appears to be specific to the Ext build.