DAVx⁵ has been successfully tested with Liberta.

Liberta.VIP is a French service provider offering a complete content collaboration suite, incl. Calendars, Contacts and Tasks. It's based on Nextcloud.

DAVx⁵ settings

Base URL:

User name and password: Please use the user name or email address and the app-password that can be generated in the Settings / Security tab at the very bottom. If you don't use two-factor auth you can use the account password instead.

Contact group method: groups are per-contact categories