Thanks for the ideas. Before posting originally, I did try various movements of the phone such as left to right, small circles, different tilts. None of these succeeded in plane detection at close range. The iPhone 15 I'm using is not the Pro, so no TOF sensor on the back camera. I did try selecting the lowest resolution format under the ARWorldTrackingConfiguration.supportedVideoFormats, hoping that perhaps that might help, but it didn't seem to make a difference to the minimum distance at which it would detect a plane. Scanning across the table at a neighboring seat does work, but makes it more difficult for the user to keep the relevant game pieces in frame. I will continue to think about this and see if I can uncover anymore detail, but if you have additional suggestions, please send them along. Thanks again for responding.

Thanks for the quick response. That is what I expected was the situation, but it is helpful to have confirmation.