Glad you are making progress[IMG class=inlineimg]/forum/images/smilies/smile.gif[/IMG].
Yes, I did wonder if part of the problem might be limited to 4K/60, but thought talking about that might confuse things when we still didn't have the basics working. Some TVs, including mine, can only do Dolby Vision up to 30fps, which since almost all movies and "quality drama" is 24fps, is just about never an issue in reality. If your Sony is one of these you will probably find that 4K/60 HDR (i.e. HDR10) does work, but DV is limited to 24, 25 & 30.
Regarding Atmos over ARC, I think the problem you are seeing is the internal app is receiving, from the stream, ATMOS in a DD+ package and simply passes it on over ARC for the 3060 to decode. The ATV insists on decoding everything itself and sending (uncompressed) multichannel PCM. Over ARC, multichannel PCM is limited to 2 channels. That's why you are not getting Atmos on your 3060 when the ATV is connected to the TV.
LG OLED65E6V, Yamaha RX-A3060 AVR, Oppo UDP-203 UHD Blu-ray player, Apple TV 4K, Sky Q 2TB, Chromecast Ultra
Home-built Ivy Bridge i5-3570K HTPC, 8GB RAM and Nvidia GTX1050 GPU with Plex and Jriver Media Centre,
Ruipro 15M Fiber HDMI cable, B&W FPM speakers, Logitech Harmony Ultimate intelligent remote.