Here are some ideas for math enrichment at home that might be helpful to you:

https://www.dcurbanmom.com/jforum/posts/list/1283364.page#30429435

Doesn't AOPS have in person classes? If he likes Beast Academy, perhaps those are similar?

Look into math competitions.

I'm looking for some advice for how to supplement my son's math outside of school which he finds very easy. He likes independent work so we have always provided him with some opportunities for self study. He scores 99th percentile on MAP/SOL pass advanced. We are not opting for Algebra 1 as I don't think it is necessary for him to speed through math courses. He has completed the Beast Academy book 5a and he took a math course via the Hopkins CTY program (he did well and they did some high school level math). He does not want to do RSM (too regimented). He likes the Beast academy books. We've done Khan academy as well. I'm considering getting him the AoPS Prealgebra textbook but I've heard that it is very difficult and can be frustrating. I want him to enjoy math. He is smart but not genius level so don't want him to get frustrated if every problem is complex!