GSI is a German non-profit physics research facility that runs a heavy ion accelerator and is part of the Helmholtz association. GSI's IT department is running a Linux "farm" with more than 1500 OS instances on premises (VMs as well as bare-metal), roughly 50% of them running Debian GNU/Linux. Debian has been GSIs main Linux distribution since 1997.
For our deployments ranging from fundamental IT services to desktops we benefit a lot from the thousands of packages that we can simply pull from the well-curated and high-quality Debian repositories installations.
We also sponsor - and utilize - the Debian LTS support.