I suppose another option is you could take the Rust route.
Garry Newman started building the game Rust in an older version of Unity. Then, two things happened: he realized that both the codebase and the design of the game itself were unsustainable and stale, and that a big new Unity version had come out mid-development with a bazillion new features. So, what he did was he completely abandoned the codebase for that current version of Rust and started work on a new one from the ground up. Then, when it was ready, he pushed released this entirely "new" version of Rust as an update to the game, and labeled the old one as "Rust legacy".
I suppose if the codebase for Among Us 1 is just such a cluster fuck but you don't want to release a sequel, you could instead just bin it as "Among Us Legacy", and start work on an entirely new one that is technically a "sequel" but still released for free to current Among Us owners sort of like an update.