Earlier quoted context omitted.
Cloudflare Email Routing is still in private beta. I'm eagerly awaiting it
It's open now: https://blog.cloudflare.com/email-routing-open-beta/
In GMail (and using Google Domains to host my DNS) I've configured this by inputting various settings as per the guide here:
https://support.google.com/mail/answer/22370?hl=en
The key relevant step is: "For school or work accounts, enter the SMTP server (for example, smtp.gmail.com or smtp.yourschool.edu) and the username and password on that account."
Is that kind of thing supported with Cloudflare?