So I think there is an issue with the arc while in eARC mode and lip sync while playing LPCM content
I have tested on an LG C9, Sony 900H and a Sony A8H.
On all of them when my Apple TV is set to LPCM output, I get lip sync issues on some content. If I change it to Dolby Digital or get the Sony to convert to DD+ it’s in sync.
it seems like there is an issue with the lip sync compensation that eARC is supposed to have when using LPCM.