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?
Yes, it's quite crazy. I found archive of old comics, the entire series of Outer Limits (1995), all ScummVM games, tons of ROMS, and books, a lot of books.