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.
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.