What about high-res audio?

The fourth-generation Apple TV introduced in 2015 dropped the optical audio output connector that had been available in previous models, relying purely on HDMI for sending sound to your TV. To keep the audiophiles happy, Apple kept the old third-generation model on sale with optical audio for a while, but that has now been discontinued, with the fourth-generation model sticking around as the low-cost option for plain old HD televisions.