Thanks for the input (no pun intended, all). Indeed, I wasn’t looking for Atmos, just 5:1. I still don’t understand why my pre-4K Apple TV won’t do multichannel streaming when it specifically offers a “Dolby Digital 5:1 conversion” output choice, but that does nothing. And again, it CAN send multichannel to the Oppo using Infuse and File Browser with my DLNA server.
Ah well, I’m lucky enough to have lots of surround discs. I better sign off before I hijack the thread with a rant about AVRs and pre-pros (too large, too complicated, wasteful rapid obsolescence …