What's preventing a library whose physical premises are closed from saying, "Okay, there are 10 copies of this book that literally nobody can get to, we'll lend out 10 e-books," using the old Controlled Digital Lending model?
That is, what about the lockdown requires moving away from the established (even if not court-tested) one-to-one basis and making a new fair use argument about uncontrolled digital lending?