I just tried it on every platform I have access to; Android, Linux, Macos, Windows and Chromebook. I was able to take a screenshot of a show playing on Netflix on every one.
Thanks. Haven't tried it on four out of five of those platforms. Last time I tried it didn't work for me on macOS but maybe that has changed. Definitely does not work on any recent iOS.
Fair use is not a right; it’s a defense. You don’t have a right to use materials for educational purposes. What happens is: you’re sued and you argue that your usage was fair use.
Because of that distinction, you technically have no right to take screenshots of copyrighted media.
Side note: the reason for this distinction is that there’s no set criteria for fair use. Some people say there’s the “10 second rule” or whatever, but they’re wrong.