I've been following this thread for quite a while - thanks to everyone who has taken the time to post details and possible workarounds. I'm a developer, so I was able to try tvOS 16 over the past week and so far, I haven't had any audio stuttering whatsoever after playing various titles from both Netflix (including Stranger Things and Drive to Survive) as well as Apple TV+ (For All Mankind, Loot, etc).
I have a wired gigabit fiber network in my home (1Gbps up and down) and the AppleTV 4K Gen2 that I use in my media room has always been hardwired. I was prepared to unplug the Cat6 due to the feedback here - but so far I haven't had to since upgrading to tvOS 16.
My previous experience with the same device hardwired on various versions of tvOS 15 was fairly constant audio stuttering unless I rebooted the device. This would help for a while and the stuttering would return.
I've also read some recent threads where it appears that Netflix is downgrading some of their streams to 5.1, but I can verify that the ones above are being shown on my Denon AVR-X4700H as Dolby Atmos.
I have both the Gen1 and Gen2 4K devices, so I temporarily swapped the Gen1 to my media room to get around the issue for a couple of months and have now switched back to the Gen2. FWIW - the Gen2 seems noticeably better in terms of video and audio quality to me so I'm happy to have it back.
Hopefully someone else here who has access to tvOS 16 can verify.