I got the ATV4K 2nd Gen and been using it for almost a year by now. and I personally regret buying it.
it might be a great device if you stream movies from streaming services such as Netflix, Amazon Prime, etc. but it is almost useless if you try streaming your own media. for example, I stream Using Kodi
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it doesn't Support HDR on Kodi (Kodi for TVoS doesn't support HDR), so all my HDR movies would play on SDR.
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it doesn't support Dolby Ture-HD let alone Dolby Atmos encoded as part of the True-HD (i.e. BlueRay content) or Kodi or external Media, it will always decode it as 5.1 only. playback.
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no support for DTS of any flavor (ATV will decode it as 5.1 PCM).
4.passthrough sound doesn't work , your ATV will always decode your media to 5.1, then transmit it to your AV receiver as 5.1 PCM All Chnl.
- you can't Install a VPN client on the ATV, hence you can't fool Netflix and other streaming services on your region to get better content library.
if i had know all this I would never buy the ATV. Apple pretty much jails you with their TVoS.
if you thinking of getting ATV and you planning also to stream external media and/or Kodi and you have a good sound system setup at your listening area, I would highly suggest staying away from Apple TV. having said that, if you planning on streaming only from traditionally streaming services, then it's a great device (assuming you not planning changing your region with a VPN or a DNS proxy, service, etc.)