Please Let Me Contact You Privately

I don’t understand this person’s threat model at all. Why do they trust the person that they’re emailing but not an email provider?

doesn't trust email because of metadata leaks

[...]

also trusts signal, which requires a phone number

That's a bit of a head-scratcher for me. Giving my phone number to signal is an absolute non-starter. I can contact you over a burner email very easily.

Can you share a bit more about what threats you're concerned about?