(OP) I'm mostly interesting in a fast hash for writing a generic, concurrent hash map.

The reference to Tries came from the original issue in the Golang repo about possible uses for a standard library hash function: https://github.com/golang/go/issues/21195

And you're right, the Trie implementation linked there was indeed a Hash-Array Mapped Tried: https://pkg.go.dev/github.com/lleo/go-hamt-key#Key