QuickStack is a self-hosted platform as a service for developers and small teams. Through a web interface it deploys applications and databases onto a k3s cluster: builds from a Git repository or container registry, automatic HTTPS, persistent storage with Longhorn, logs and a web terminal, monitoring, scheduled backups to S3-compatible storage, Postgres, MySQL and Redis from templates, per-project permissions with two-factor authentication and SSO, and extra nodes for a cluster. It is a self-hosted alternative to managed platforms such as Heroku or Vercel and is open source under the GPL-3.0 licence.
QuickStack is developed by achtpunkt GmbH in St. Gallen, Switzerland, which also builds custom software. Switzerland is not an EU member but an EFTA country with an EU adequacy decision for data protection. Because you install QuickStack on servers you choose, data location and jurisdiction depend on the hosting provider you pick; the vendor describes no hosted offering. No parent company is stated. You remain responsible for updates and operation of the host.