Swift! It actually has a pretty big server community, Vapor and Hummingbird are both great frameworks, Apple has been replacing some of their Java services with it, it's open source and cross platform and Apple seems serious about making it viable on Linux, which it is. No need for Xcode, it has an open source LSP and first class VSCode plugin.
Plus it's a fun language to write. Some people say it's a nicer, higher level Rust.
I also like the look of Kotlin but I've never used it. I think Kotlin and Swift are the two premier modern multi-paradigm languages.
I do like Swift but it also suffers a bit from identity crisis. The compiler experience is quite disappointing too—I found myself helping the compiler more than the compiler helped me.
I've since moved to Rust and have not looked back. Importantly, rust-analyzer runs circles around the Swift VSCode plugin (or Xcode for that matter)
The identitiy is clear, it is a language first and foremost for Apple ecosystems.
It also needs to target GNU/Linux, because Apple got rid of their server offerings, thus anyone doing server code for applications on the Apple ecosystem, that wants to stay in a single language needs to be able to write such software on GNU/Linux with Swift.
Windows well, since they have the open source story, it kind of falls from there as complement.
On the revamped website they are quite clear about the identity.
Cloud Services, CLI and Embedded as the main targets for the open source version.
I'm the same but opposite, I like Rust but find myself using Swift most of the time. They sort of do the same thing but coming from opposite directions. Can't go wrong with either imo.
I really do wanna try Kotlin at some point as well. Rust, Kotlin, and Swift feel like the future of languages to me.
Plus it's a fun language to write. Some people say it's a nicer, higher level Rust.
I also like the look of Kotlin but I've never used it. I think Kotlin and Swift are the two premier modern multi-paradigm languages.