Well if you know of a simple way to target - reliably - a high-quality crypto lib that can access any underlying OS entropy source to generate a decently random number, with WASM, please inform us of it here; it'd be great to know.
Though admittedly, it seemed terrible if there wasn't, so I would be happy if the post can be proven deficient. I'd have ordinarily assumed many options available in the .js ecosystem, instead accepting it's a WASM OS-access issue.