Swift on Server has become quite mature over the past years. The ecosystem features a libraries for a lot of tools you want to integrate. Furthermore, it is being used in production by some major companies besides Apple, e.g. Amazon has a bunch of production services running on it.
One of the greatest things about Swift on Server is not only the language but also the community. They are very open to new joiners and try to help whenever possible. Furthermore, with the latest Swift features such as Swift Concurrency it looks even more promising.