Images Not Displaying in TwentyTwentyOne Theme

I’m a long-time and very happy display-posts user, deploying it on several websites without any problems until switching to the new TwentyTwentyOne theme as I overhaul my personal site. I’ve stripped several test pages down to the most basic shortcode, but images do not display at all when the display-posts plugin is used in this theme.

I can swap out to virtually any other theme without error, but this latest theme, though lovely, breaks the plugin. I realize it modularizes things in a significantly different way with template parts, but I cannot imagine how that is interfering with something as basic as the featured image, which is embedded in every post.

I did create some CSS classes to control the formatting, but stripping those out completely didn’t make a difference. The images still would not display.

I’m running pretty lean on this particular website, with very few plugins. Even shutting them all down doesn’t seem to solve the issue.

Has anyone else encountered problems with images not displaying when using the display-posts plugin with the new TwentyTwentyOne theme?

Thanks a bunch for any insight folks might be able to provide in troubleshooting this!

Gratefully,
Sue.

The page I need help with: [log in to see the link]