Using an S5 running LineageOS (android 7.0.1)
To move the contacts from your local addressbook to your DAVdroid account (and thus your CardDAV service), you may either:
export your Android contacts from your local account (Contacts / Export to .vcf file) and import them into your DAVdroid account (Contacts / Import from .vcf file)
I don’t see any option in the app to import from contacts to davdroid account. I’ve got local contacts on my phone or a vcf file I’d like to use. My cardDav server is on my nextcloud server. I can’t simply import the contacts to nextcloud because I get an error saying my vcard file is not version 4 or 3 (tips on how to convert my vcard file to one of those versions is welcome too).