As a test I created a gallery called test gallery.
Then I gave some of the items in the gallery links
I created a summary block on another page that uses the gallery as the source of its images.
Then I created a css rule to kill pointer events for any summary items whose link is from the original gallery (begins with /test-gallery).
It works as expected. Items with no clickthrough url have a standard cursor and are not clickable but those with a clickthrough work properly.
Here is the code - insert it at the bottom of your custom css area after any other code that may already be there. You'll need to tweak href ^= "***" to reflect your gallery slug
.summary-item a[href^="/test-gallery"] {
pointer-events: none;
}