While I couldn't find a specific Internet Archive link for Avengers: Endgame (as it's a copyrighted work and not publicly available), I can discuss the implications of such a link existing.
The Archive also hosts a massive collection of public domain films, classic cartoons, and home movies. However, a common misconception is that everything on the Internet Archive is free to download. This is false. The Archive respects copyright law. While you can find Night of the Living Dead (1968) there legally, you will not find Avengers: Endgame hosted officially. avengers endgame internet archive link