This is truly great news! I recently migrated my email and calendar from Google to Proton but decided that Drive is useless for me without photo backup on mobile. Linux client with sync is also extremely important but AFAIK Proton Drive is supported by Celeste so this might be a viable workaround (though I didn’t test it yet).
I also want to point out that during the short period of time when I’m using Proton Mail and Calendar, they already received a few new features. If they can keep up with this pace of development then I’m honestly fine with paying for incomplete services just to support them.
I really hope Proton will become a one stop shop for secure online services. Fingers crossed!
This is great news but I just have to say it: we need Proton Drive on Linux. Still very happy though.