DAVx⁵ has been successfully tested with Disroot.

Disroot is a community-driven and privacy focused service from Amsterdam that uses Nextcloud as a backend for its cloud. It's principles are based on federation, decentralization and freedom.

DAVx⁵ settings

Base URL: https://cloud.disroot.org

User name and password: Use the same email address and password which you use in the webmail login (either your @disroot.org email address or the user name). You probably need to create an app-specific password (cloud.disroot.org → Security tab → App password) if you use two-factor-authentication on login.

Contact group method: groups are per-contact categories.