I mean it! In the Los Angeles area at least two channels, 5 and 30, have subsidiary channels. Channel Five’s subsidiary is “This,” which plays old movies; Channel 30 hasd a sub-channel called something like “Qube” and geared for children.
But no newspaper has listings for such channels. And forget TV Guide…They don’t care about local programming anymore. 
Try searching “Titan tv” in google. You’ll have to set it up for your location and tell it whether you are looking for a cable system or broadcast channels or whatever, but once it’s set up it works pretty well.