I am curious about that too.
Where did Daily Open Challenges Move To?
See the Help & Support Forum where I also posted this question which was answered. Also, it looks like this has been fixed and looks like it did before this change.

On my Macbook Air, I can no longer find Open Challenges for Daily Games. When I select "Daily Chess" then "New Game Play", the resultant screen format no longer no longer includes open challenges. Here is the new screen format which does not allow open challenges:
It's under Custom Game and Open Challenges. They show up on the right side of the graph.
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On my Macbook Air, I can no longer find Open Challenges for Daily Games. When I select "Daily Chess" then "New Game Play", the resultant screen format no longer no longer includes open challenges. Here is the new screen format which does not allow open challenges: