ANYONE WHO NEEDS HELP UPDATING THE GAME WITHOUT STEAM
Many people seem to be asking how to update the game without activating the Steam key. Many people reply with "activate your Steam key"; that also works. However, I assume if you bought the game off Itch.io, you would prefer to use that DRM-free copy, as do I.
The Itch client is for the most part just a glorified browser. However, it is useful for updating games such as Among Us. I suggest you download and login to the client. Then download Among Us via this client. After that, navigate to your library and click on Among Us. It should then load up this page which you are reading on right now - the Among Us page. In the bottom right, right next to the big "Launch" button, there should be a little cog button. After pressing that button, a window will pop up. Press "manage". From there you can press check for updates and the Itch client should handle it for you.
Let me know if this helps and please do upvote this comment so that people see it because I've already replied to several comments.