Working in IE/IR, I probably get this question more than any other, and it's so complicated because a) the answer changes almost every time a student adds/drops a course, and b) every questioner means something slightly different. The most precise method I've come up with involves exporting an enrollments report and using a nested =IF(SUMIFS) formula to create all the categories that different questioners are interested in.
My dream is that at any given moment, I could go to Academics > Academic Term > Students and filter for Delivery Method is "Exclusively distance education" or "At least one but not all distance education" or "No distance education" (to match the categories in the IPEDS "12-month enrollment by distance education status" preset report), and it would return those students based on the delivery methods of the courses in which they were enrolled for credit. This would be tricky with students who were using multiple delivery methods across multiple programs, but it would be so incredibly amazingly helpful if this were available.