I entered a new contact on nextcloud, then edited it on the iPhone, then used the iphone’s map app to locate the place. The phone numbers are OK, but Apple seems to be extending the vcard vocabulary for its own purposes:
item1.ADR;type=WORK;type=pref:;;redacted
item1.X-ABADR:US
item1.X-APPLE-SUBADMINISTRATIVEAREA:redacted
item2.URL;type=pref:https://www.redacted.com
item2.X-ABLabel:_$!<HomePage>!$_
X-ABShowAs:COMPANY
It might be nice if nextcloud extended its vcard vocabulary to show these, even if you don’t allow users to generate new fields with them.