Setting up Home Theater with AppleTv4

Hello - Just when I thought I knew a thing or two, I don’t! If anyone can give me some advice I’d really appreciate it. I replaced my first generation Apple TV with #4. Of course it’s now apples and oranges, no pun. Gen one Apple TV had an optical cable that connected to the sound system. Gen 4 eliminated optical and utilizes USB-c. I’m connecting to an older Harmon Kardon HVR 140, which uses the very old fashioned white, yellow and red cable connectors, or optical.

I purchased a cable that has three plugs (red, white yellow) on one end and USB on the other and an adapter to convert USB to USB-c. It should all work, and it doesn’t. Anyone familiar with Harmon Kardon - I’ve plugged the Apple TV to Video 2 Audio/Video input. Any Brainiacs available? I’m stumped.
All of the new streaming devices nowadays are all targeted at the "Gen Y" consumer who just wants to plop a panel on the wall and a streaming device so that he can do "Hulu" or whatever and he's good to go.  These are no longer designed with the audiophile in mind.  All the devices are like this (AppleTV, Roku, Fire TV).  The USB-c port will not do a digital audio output.  For Apple, it's meant for diagnosis and service/support only, which makes it completely useless to you.

Your only option is to get a new receiver that supports HDMI, because that is the only way you will be able to get audio out of the AppleTV device.
I had a similar problem where I had previously used the optical output on the Apple TV to connect to a pre-amp/DAC. When I upgraded to the 4K Apple TV I connected the Apple TV directly to a Vizio 4k TV, fortunately for me my 4K TV had an optical out socket. Effectively passing HDMI audio from the TV to my pre-amp/DAC.
Another alternative I just thought of is to look into the Sony Blu-ray players.  They will have built in streaming apps for Netflix, Amazon and (I think) Hulu.  Maybe a few other services.  The upper models have digital COAX output (much better than toslink) and are highly superior streaming transports when compared to AppleTV and others.   That b big said, you cannot install any old app like you can with AppleTV or Amazon FireTV.
There's no USB-C port on the AppleTV4; that's an HDMI port.