Earlier this year, Google made a change to the web version of Duo that meant you could log in and start a call without having a phone number linked to your account. This made it easier for you to start a video chat but didn't help others get in touch with you. According to Jane Manchun Wong on Twitter, Google is working on a toggle that will allow people to contact you on Duo even if they only know your email address.
While digging into the Android version of Duo, Wong uncovered the option to make you 'Reachable with email address' and says Google is currently working on it. This would open you up to calls from far more of your contacts, even those you may not know that well but who happen to have your email address, but you can just leave it switched off if you're not comfortable with that.
Google Duo is working on “Reachable with email address” setting pic.twitter.com/BbCiOhoW0Z
— Jane Manchun Wong (@wongmjane) April 30, 2020
It's unclear if you'll also be able to log into Duo and make calls on an Android phone without linking your phone number, as you can with the web version now, but adding that functionality at the same time would seem to make sense. There's no telling when the new option will be rolled out, but it's unlikely to be too far out. With other new features such as larger group calls better low-bandwidth performance, Duo is maturing exactly when we need it the most.