Look at ContactPicker API for integration with Solid Contacts

See

https://developers.google.com/web/updates/2019/08/contact-picker#security-considerations

"Access to the user’s contacts has been a feature of native apps since (almost) the dawn of time. It’s one of the most common feature requests I hear from web developers, and is often the key reason they build a native app.

The Contact Picker API is a new, on-demand picker that allows users to select entries from their contact list and share limited details of the selected entries with a website. ..."

Look at

• Using this API in Chrome to allow a user to import their existing contacts into Solid
• Implementing the same API in Solid to allow future developers to access user's solid contacts

Note that the contact picker API is, deliberately it seems, not rich in the data. It drops things like home/work/.mobile distinctions for phone numbers. So VCARD import and DTP (and other APIS) may be the best way of importing whole contact databases.

Start with the linked Contact Picker API documentation, especially its security considerations, and inspect the contacts-pane entry points for contact import and external access. Evaluate Chrome support for importing existing contacts into Solid and the feasibility of exposing Solid contacts through the same API. Done means the integration approach and limitations, including reduced phone-number detail versus VCARD or DTP, are resolved.