I did mine online when I got it on March 12. I suspect the vast, vast majority of people will respond online. If not, they'll get a paper form to submit.
And if they don't send that in, they'll get a visit from a census worker. The visiting part is what I find worrisome, given that it means personal contact during the virus period.
This article explains how college students are counted in the census, even if their school is closed:
https://www.monroenews.com/news/20200316/census-explains-how-to-count-college-students
It essentially says that college students are counted in their college town. If Starkville's population is 25,000 and there are 22,000 students, does that mean that Starkville's "real" permanent population is only 3,000? I don't think so.