“We’re working on constantly shifting grounds,” said Rudolf Frieling, a curator of media arts at the San Francisco Museum of Modern Art, which has been at the forefront of sustaining online art. “Whatever hardware, platform or device we’re using is not going to be there tomorrow.”

“Frankly speaking,” he added, “it’s a huge challenge.

Not every museum is set up to do that. It takes huge technical expertise.” The riddles are only solved by “actually doing it,” Mr. Frieling explained.