While some universities might offer *some* components of a doctoral program (including a DLitt, if they offer it at all) online, the core research, thesis writing, and supervision are almost always expected to involve substantial in-person or at least highly interactive online engagement with faculty.
If you find any institution claiming to offer a full DLitt online, proceed with extreme caution. Thoroughly research the institution's accreditation and reputation before enrolling in such a program. The legitimacy and value of such a degree would be highly questionable.