eARC from Samsung TV to AppleTV 4K (gen 2) and HomePods Duo not working after tvOS 26.01

After installing tvOS 26.01 on an AppleTV-4K(gen. 2) and updating a HomePod Duo, it worked with my Samsung TV only if the AppleTV was set as the "source." It didn't work with my TV set with my CableTV as the "source" even thought the TV sound was set to use eARC for sound output.

The solution was to re-setup my AppleTV according to <Use HDMI ARC or eARC with your Apple TV 4K - Apple Support>. I found that using eARC on the AppleTV had somehow been turned off during the tvOS 26.01 update.