Here are some gc crates:

https://docs.rs/rsgc/latest/rsgc/

https://docs.rs/ristretto_gc/latest/ristretto_gc/

https://docs.rs/dumpster/latest/dumpster/

https://docs.rs/shredder/latest/shredder/

I have no experience with them. In any case, it would be advisable to make the GC implementation swappable so that the language is gc-implementation-agnostic.