The iOS Developer Community Survey has a section which asks respondents to rate their current adoption of Swift for building applications that will deploy to a server environment. The adoption is quite low (~3%). One highly rated standout though, is the Vapor Framework for building web applications in Swift.
The survey results of similar programming languages (Go & Rust) show that building web applications is by far the most common activity for software developers and interestingly, both the Go and Rust Developer Surveys indicate that Linux is the preferred platform for developing on, not just deploying to.
Other types of applications built in Go and Rust include interactive command line tools, deployment scripts, agents for monitoring running environments, data extract, transform and load tasks and many more. Swift is a candidate for building these types of applications as well.