Hi @natemp21
Thanks for your post!
This will be happening due to the various CEC settings on your devices. On both the PS5 and the Apple TV, look for settings that are along the lines of “turn on the TV when device is turned on” and disable them.
It doesn’t really have anything to do with the Arc - more the sources and TV.
You may need to look at the TV settings as well. Many TV manufacturers rename CEC, but Googling “CEC” and the name of the manufacturer will tell you what your TV calls it. On the TV, it needs to be on for audio to come through the Arc, but there may be some additional settings.
What I think might be happening is that when you turn on the PS5, it turns on the TV, and the TV then turns on attached devices, like the Apple TV. The same will happen with the Apple TV being turned on first. Though it could just be the source devices turning each other on (uh, that sounds weirder than I meant it to).
I hope this helps!