I asked professional recruiters about hiring for this role and they told me the same thing as our engineers: that I'm searching for a unicorn that barely exists

I asked professional recruiters about hiring for this role and they told me the same thing as our engineers: that I'm searching for a unicorn that barely exists, and they didn't feel confident in being able to deliver a candidate for this. And this was talking to boutique technical recruiters for startups, not big generic firms.