It's a little ironic that privacy.com is asking for your SSN lol.
There is no way around know your customer, but that doesn’t mean “requires SSN”. That’s just the easiest path from point A to point B and most businesses don’t care to support anything else.
[1] https://www.irs.gov/pub/irs-pia/id-me-pia.pdf (Pages 2-3)