@ro Yeah, funnily enough I was grappling with that issue last night! I just exported my Google contacts for now, but I'll need a CalDAV or similar solution going forward - unless Proton change their policy.
@dajb @ro I moved to Proton 7 years ago and completely de-googled 3 years ago. One thing I had to accept was having a contacts list for emails and a separate one for phone numbers, which is just on my phone and also visible to Signal and SMS.
I have the Protonmail app on my phone. Every couple of months, or when I get anxious, I back up my phone contacts to a vcf file.
I'm not aware of this arrangement being difficult or clunky - but possibly I've just got used to it. Tho I don't remember it being clunky even at the start.