I would guess that ebooks are fine. It's been a long time since I looked into this, but as I recall the important distinction the research found was more like, "Multimedia purely for the sake of multimedia seems to be verschilmmbessern, because it tends to inhibit the kinds of deep cognitive processing that lead to effective encoding."

"Screens = bad" seems to be, as far as I can tell, the kind of unhelfpul massive oversimplification that always happens when science gets filtered through the rumor mill. Because the truth is too nuanced to make for a fun anecdote you can tweet or share in light social conversation.