As of September 30, 2023, reached its "End of Life" status. Here is what that means for you:
: If you already own the game, you can still download and play it. Marvel’s Avengers Endgame Edition Free Download
: Fake login pages designed to steal your account info. As of September 30, 2023, reached its "End of Life" status
: Look for legitimate third-party key retailers (like Humble Bundle or Green Man Gaming), though stock is extremely limited since the delisting. As of September 30
If you want to play the game now without risking your computer's safety:
: Check if a friend can use Steam Family Sharing to let you play their copy.