The biggest culprits are five: artifacts, clones, conda, packages and registries. Each list between 20 000 and 30 000 files.
These numbers remind be a bit of suckless philosophy and leave me wondering if it needs to be this way.
My current solution is to set JULIA_DEPOT_PATH to a NAS with out limitations on the number of files before starting julia.
At least on our cluster, not everyone has access to such a storage. Most users must live with smaller numbers of files.