I'm having a similar issue with my LG television. Access to the alternate audio channels is only available via the quick menu's "Multi-Audio" item, and it fails to list streams such as WNED's radio feeds, even though it happily picks up any old alternate-language feed whether it's a proper extra tongue or description track, or just a downmatrixed mono feed. Worse, I can't seem to locate any troubleshooting information for my TV model related to this issue.

I have a sneaking suspicion that the firmware, at least for my TV model, does not properly implement SAP enumeration.