Apple TV Latest generation - downgrade tvOS to 11.2.1

Hello,

I have the latest version of AppleTV 4K, which does not have a USB port. How can I connect this device to my computer and use iTunes to downgrade tvOS from the current version to an earlier version?

I am looking to utilize a feature which was removed after 11.2.1 (audio passthrough to a home theater receiver).

I don't see 'downgrading' as a breach of any EULAs, so I feel it's a fair question to ask.

Can someone provide guidance?

Thanks

Bob