There are many, many threads relating to Among Us not being accepted to speedrun.com.
I'd recommend you read this thread for a more in-depth explanation on why Among Us will never get accepted: https://www.speedrun.com/the_site/thread/hsffi/2#vrsq5
And it will still never be accepted in its current form.
The site isn't interested in online, unending, or pvp oriented games that game moderators can just make up on a whim endless and arbitrary categories for free WRs.
There is nothing stopping you or any of these people from making a board to keep track of all of these made up runs. Theres among us forums already in existence that could do just that. It just won't be here unless the game changes significantly.
The general consensus that we came to was that Among Us is a primarily PvP game, which we don't accept. And the freeplay content is too short and simplistic for us to consider making a leaderboard for it. That being said, you don't need to have the leaderboard on the site in order to run the game. There are a couple games that have good sized communities for games that we rejected from the site, most have discord servers for the community and track records on google docs.