The easiest way to install Done is directly from the Nextcloud App Store:
Apps
Applications
Enable
You can also find Done published on the official Nextcloud App Store
git clone https://github.com/the-done/nextcloud-done.git
mv done /var/www/nextcloud/custom_apps/
occ app:enable done
make build
Automated managerial reporting.
Dashboards and analytics.
Calendar, Deck, Tasks, Mail, Files integration.
Per-project sync with task management systems.