If you don’t require deterministic hashes (and deterministic hashes are bad for anonymization anyway) just hash data+randomBytes(16) (obviously, don't save randomBytes(16) anywhere). There you are, nobody can bruteforce your hashes.
Even better, just replace your data with H(randomBytes(16)). Or a random UUID.
Umm what good is the string of random bytes if you don’t store it anywhere? The point of a one-way function is that its output is verifiable given the input.
Even better, just replace your data with H(randomBytes(16)). Or a random UUID.