I contacted HBO Now customer service yesterday, asking about if they finally supported Dolby 5.1 on Android TV. They claimed they did, but then I remembered a month or two ago testing it when they claimed they supported it but then clarified that this was only on Sony Android TVs. I questioned further and received this:
Hi Andrroid,
Thank you for reaching out to HBO NOW Customer Support. I understand you have some questions regarding Dolby 5.1 for the Android TV.
Android 5.0 and later
Supported devices:
- Nexus Player
- NVIDIA SHIELD
Thank you,
Alexander S.
HBO NOW Customer Support
This looks like a scripted answer and he didn't actually understand or bother to research your question.