I decided to report an old problem again. I have never been able to connect TCL 49S405 with Yamaha RX-V575 using HDMI ARC and Dolby Digital Plus. It works with straight Dolby Digital, DTS but the moment I select Auto Detect or Dolby Digital Plus, I lose all sound. I even lose the beeps when moving around the menu so it is not specific to any particular channel. It is either Roku TV or Yamaha AVR problem.
The AVR is detected and documented as DD+ capable and there is a way to re-sync Dolby Digital Plus connection temporarily. I have to cycle through the AVR inputs and back to AV4 (ARC) to recover DD+ audio but only until a stream switches to something else like another channel or an advertising block when the DD+ connection is lost again. It feels like this problem has a simple software fix - TV an AVR must communicate when the stream switches. As a workaround I am using Dolby Digital (without Plus) because re-syncing manually is not practical.
I had this problem since 2017 and it has been reported with other receivers and sound bars by many people, search this forum for DD+ or Dolby Digital Plus. I understand why this might be a low priority bug - who'd use a budget TCL TV to set up a home theater with an AVR, but still. This might be Yamaha AVR problem - if you have DD+ working with another receiver, please do reply.
Let's hope that we'll get some attention from Roku engineers this time.