IIRC, the initial Munich Linux Project ("Limux") from 2004 I think was somewhat of a failure. They spent millions migrating dozens of different Windows applications, but found that certain offices (e.g. the land registry) kept using Windows applications for obscure hard-to-replace services and databases, leading to friction.

Later they rolled back then entire migration just to re-announce a new Linux migration more recently, see https://www.zdnet.com/article/linux-not-windows-why-munich-i...