While watching some videos on YouTube I found out the Dolby Digital Plus to Dolby Digital conversion is not available, otherwise the "5.1" logo on Netflix would be always visible (like the Nvidia Shield 2019), it only supports Dolby Digital Plus passthrough unfortunately.
It can't compete with the Fire TV Stick in that regard, so let's see if the new Chromecast device stacks up.
have you heard if the new chromecast does it yet?
I think there's a fundamental issue here. These TV sticks / boxes should actually support older audio output formats like DD. This is because such devices would most likely be used with older TVs that don't support DD+. In newer TV (say models after 2017), most of streaming Apps / cast / Android are inbuilt; hence, it's less likely one would us a TV stick with a newer TV.
The Netflix in PS3 or older BD players can give the DD 5.1 although those devices are not having DD+ audio output. I'm still not sure Netflix Apps on such devices are somehow DD compatible or devices are converting DD+ to DD at the audio output over optical / HDMI (I've tested both working directly to sound system or via TV). If the latter is possible, I believe TV Stick / box makers should be able to do this with a firmware patch.
Fire OS is an ad supported garbage.