It took me a bit, but I finally figured out how to get full surround (5.1) sound on broadcast channels (either live or recorded) using my Roku Express 4K+ with the Tablo app. Under (Roku) Settings->Audio->Digital Output Format, change Auto to Custom, Dolby Digital Plus. So far, so good for those channels.
However, none of the streaming channels are giving me surround sound and certainly some of the shows that are being streamed did have surround sound when they were originally broadcast. Has anyone gotten surround sound from a Tablo streaming channel?
My Tablo is a 4th generation one.