Hi

In the UI, on the Templates page, add a "Systems" column showing how many attached systems a template has.

On first load from content-sources this information would not be avialable so show a spinner or loading indicator.

Take the list of UUIDS (no more than 20 or 50 or some small limit), and request them from patch, adding the system counts to the table as its returned.

Test the limit to make sure it works.  If there is more than the limit, request more batches of UUIDs until the table is fully populated.