Many modern TV's, especially 'smart' TV's are able to automatically adjust their panels frequency/refresh rate to match the frequency of source content.
However (unless things have changed in recent years), computer graphics cards puke out a fixed frequency/refresh rate - which would have to be manually adjusted (if supported) to match the frequency of source content.
That being said, there's way too much content out there that's been poorly encoded and incorrectly flagged. So it's always good practice to check the source content for errors!
EDIT: It may also be worth pointing out that 24Hz (24fps) encoded content is actually pretty rare, even on UHD disc's. Indeed, most (progressive encoded) movie content runs at 23.976fps (ie: 23.976Hz). And if you force content encoded at 23.976fps to be displayed at 24Hz, it introduces other issues
