It's legitimate.
Proton hasn't updated their official phishing advice page with the new domain, buuuuuuuuuuuuuuut you can see them suggesting someone contact them on the protonme.zendesk.com domain on their official App Store page (under the "the app changes fonts on internal website" review), and on their official Google Play Store page (has to be set to the turkish language in that URL otherwise the review they're responding to doesn't show up)
Unless BOTH accounts that manage their app distribution on both the Google Play AND Apple App Store were quietly compromised (and never found out), and used to post just a handful of replies to reviews with a phishing domain, I think it's safe to say it's legit and they just forgot to add it to their list of non-phishing domains yet.
