Exchange Visitor (J-1) programs must be predominantly in-person.  The U.S. Department of State defines predominantly as 60% in-person. Exchange visitors may participate remotely no more than 40% of their program when the host department has instituted partial remote policies and their faculty supervisor has approved their hybrid program participation. For example, if the visitor is invited to do research 5 days a week, then only 2 of the 5 days may be conducted remotely or by tele-work. The rest of the time will require in-person presence at the site(s) of activity.

U.S. Department of State Guidelines on Remote Policies