I was also interested in server sided Swift for a bit but didn't go very far with it. Java is the "obvious" choice for statically typed web backends. Personall

I was also interested in server sided Swift for a bit but didn't go very far with it. Java is the "obvious" choice for statically typed web backends. Personally I'll recommend Go and C#. Both have a low learning barrier to entry, check your boxes for backend languages, and have ample resources online. I would choose C# (on ASP.NET Core) if you want flexible typing and inheritance, and Go if you want "simple" imperative code. Rust is also popular but I don't know enough to comment on it.