Is it widely known that Thanos caused half the people to disappear, or is it just regarded as an unsolved mystery to the general public?
Is it known that the Avengers were responsible for undoing it?
In Avengers: Endgame, Steve Rogers is in a support group meeting for survivors and, if I recall the scene properly, the snap and Thanos are known.
"The world is in our hands. It's left to us guys. And we got to do something with it. Otherwise... Thanos should've killed all of us."
In Spider-Man: FFH, there are a lot of signs about the entire world mourning Iron Man, thanking him for giving his own life to kill Thanos. The entire plot of the movie is about who should bear his legacy to inspire hope all around the world and why Tony chose Peter Parker.