Yes you CANNOT daisy chain ATV4k to an Oppo and then to your AVR. Also do not connect ATV4k directly to TV and then daisy chain backwards to the AVR.I have Apple TV 4K connected to the input of Oppo BDP-103D and then output to Denon Receiver. Upgraded the Tidal app. It shows the Atmos tracks but says the device is not compatible and will play in stereo only. All the cables are the latest format. The Apple TV should really be connected directly to the TV and then to the receiver, but the TV will only passthrough stereo to the receiver. Apparently, some newer TV's pass through some surround formats, but it is not universal and very hit and miss and only apparent after you purchase the TV despite what it may say on the box. The Apple TV really needs two HDMI outputs one for video and the other for audio, as earlier models used to have with an optical output. Problem is most people don't notice and can't tell the difference, so there is not a lot of motivation. Maybe in the next model. I have tried to explain the problem to my wife and adult children but they look at me like I just arrived from Mars. We have six Apple TV's (2x 4K and 4x4) in all and they are used for almost all TV viewing. It is by far the most mandatory device within our extended family. I've cancelled Tidal till they sort it out. The content so far is not exciting enough to spend too much time on it. Most Atmos audio on the 4K Apple TV's attached to Video content downscales to multichannel or at least Dolby Digital 5.1 with no problem. On the Apple TV 4's, it plays as DD 5.1. This is not happening with Tidal. Probably works with all equipment NEW, but that's not going to happen. If anyone else has more success using an Oppo in the chain, I'm interested to know how you did it.
Direct handshake then? Bummer!Yes you CANNOT daisy chain ATV4k to an Oppo and then to your AVR. Also do not connect ATV4k directly to TV and then daisy chain backwards to the AVR.
ATV4k needs to directly connect to HDMI HDCP 2.2 on your AVR. Also Make sure your Tidal app is updated to May 26, 2020 version otherwise you'll only get 2.0.
Also an optical output would defeat the purpose and you'd only get 2.0 out of optical, Atmos cannot be passed via toslink, due to DRM.