I recently found a switch that works....FINALLY. I tried a few different ones recommended on here. Including ROOFULL 5 in - 1 out 4K 60hz HDCP 2.2 switch, a Kinivo 550BN 4k switch. Both had handshaking issues with the HDMI output. I would occasionally get a black screen. They both worked if I had turned my TV on and off a few times with the soundbar turned on. Eventually I could get it to work. I have a LG B6 OLED for reference btw. The soundbar is on the latest firmware as of this post.
But FINALLY, I found one that works perfectly!!! It was on this thread as one to try but nobody seemed to give it a go. I took the plunge only because of the issues I had with the above two switches.
Here is the info -
ViewHD Model: VHD-UHD4X1A
4 In - 1 out
If you search by that model it should work, just in case the link gets deleted. I hope this also works for someone else!
I also discovered the HDMI going from my switch to the soundbar had to be perfect for my ATV 4K to work on 4K @ 60hz HDR chroma 4.2.2. All of my other 4k sources (comcast, xbox, PS Pro) worked fine, it was just the ATV that was being a pain. So I tried several different cables I had, even a "premium ultra high speed cable". It would work on 4.2.0 chroma but it was unstable when I tried the check HDMI connection feature on the ATV. I tried a different cable and had artifacts, another one gave me flickering. Either way, it seems the soundbar is VERY picky about HDMI cables. I had bypassed the soundbar last night using the same premium cable that was causing my issues direct to my TV. Worked flawless but as soon as I ran it through the soundbar, all these issues came back. Long story short, I am now working flawlessly with the HDMI cable that came with the sound bar between the switch and the soundbar itself and then one of my premium cables going from the soundbar to the TV.
I ran the check HDMI connection feature multiple times with it on the highest bandwidth setting on the ATV (4k @ 60hz HDR 4.2.2). Absolutely zero issues. I even watched 4k content on multiple sources last night and no artifacts or flickering or anything. I have the switch set to EDID auto & ARC OFF.