I couldn't find the Flintstones movie from 1994 anywhere but googling it I found it here https://archive.org/details/the-flintstones_202304 and you can either download it via torrent or directly. On top of it it says that the movie is CC0 which means Public Domain. But that can't really be, it's only 29 years old.
That must be pirated, or not?
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No it's all very, very good :)