I was trying to search for animated GIFs separately and don't see a way to. I searched for it in this forum and the last post is ten years old and I wonder if there is a way now. I'm slightly disappointed I can't as DOPUS is able to tell them apart when it renders a thumbnail for it adding a sprocket overlay.
ExifTool can report the number of frames a gif has, so ExifTool Custom Columns should let you display and search on it within Opus.