Well that blows. I just set up a proton mail account and was going to migrate from gmail.
But on the other hand, I gather that Mozilla has picked ProtonVPN for its integrated VPN testing. And they seem competent and privacy-friendly.
Also, whatever they did with ProtonVPN, there's no reason to believe that there's anything wrong with ProtonMail. That's arguably their core competency. And they arguably brought in Tesonet because VPNs were not part of their core competency.
But they do seem more privacy-friendly than most.
[0] I use migadu.com but fastmail.com seems to be very popular with the HN crowd.