In this photo on my Apple TV 4K I just selected Season 42 and attempted to move right to select the recorded episode, but focus stays on Season 42 so I cannot play the episode.
I suspect it's because there are not any episodes directly to the right of Season 42 as this problem doesn't occur with the other seasons which have multiple episodes recorded.
The HDHomeRun app shows Version 20260817 for both App and UI.
This issue might already be fixed as I can use the cursor-right key on my Mac Studio where HDHomeRun shows Version 20260915 for App and 20260908 for UI.
I did check if there was an update available on the Apple TV but it shows 20260817 as the current version.