Lightroom doesn’t appear to provide a good built-in overview for this. Based on the community response, there isn’t an easy way to list all publish collections with pending updates.

A practical workaround is to organize all collections for a publish service under a top-level collection set such as “All.” Then you can click through that grouping and republish from there, instead of hunting through every individual collection separately.

So the short answer is: not really—Lightroom’s Publish Services can show pending items within collections, but there isn’t a convenient global finder for all collections with unpublished changes.