Since you’re asking about developing a list, I assume (hope) this is for next year. My D is in the same boat and I assume campuses will be open for visits sometime next summer. Not ideal, but there should be time, after narrowing down the list based on factual data, as noted above.
Visits can occur as late as April 2022, though it may require a few more applications if your can’t eliminate some schools based on visits prior to applying, so that’s a fairly long period of time.
I do feel bad for students applying this year who didn’t get a jump on visits before this Spring. From my older D’s search, campus visits are quite important. Facts, glossy booklets, and slide shows can’t give you the same feel. She quickly narrowed her list to two where she would “fit” based on visits.