I do photoshoots for people to view and select photos online. When they heart a photo online, how do I go through the photos and either sort or create a smart collection for photos that they have hearted?
Are you using Lightroom or Lightroom Classic (you mention Smart Collections, which are only available in Classic)? Neither app allows you to sort specifically by "likes" or "comments", though Classic does allow you to sort by "Last Comment Time", so the most recent likes/comments would appear at the top of the grid. Also any unread comments or likes would have a yellow badge icon in the Grid view.
Lightroom now shows the comment or like icon on the thumbnails is the Square Grid, but offers no way of sorting on them. However, they will also be reported in most recent top-down order in the Notifications panel.