Can you Run Xcode in Linux?

I really wanted to comment, not answer. But just to be precise, OSX is not based on BSD, it is an evolution of NeXTStep. The NeXTStep OS utilizes the Mach kernel developed by CMU. It was originally designed as a MicroKernel, but due to performance constraints, they eventually decided they needed to include the Unix portion of the API into the kernel itself and so a BSD-compatible "server" (originally intended to process requests for BSD-compatible kernel messages) was moved into the kernel, making it a Monolithic kernel. It may be BSD compatible in the programming API, but it is NOT BSD.

The rest of the OS involved ObjectiveC (under arrangements between Stepstone and Richard Stallman of GNU/GCC) with a GUI based on a technology called "Display Postscript" ... sort of like an X Server, but with postscript commands. OS X changed Display Postscript to Display PDF, and increased the general hardware requirements 1000 fold (NeXT could run in 8-16MB, now you need GB).

Due to the close marriage of GCC and Objective C and NeXT, your best bet at running XCode natively under Linux would be to do a port (if you can get ahold of the source - good luck) utilizing the GNUStep libraries. Originally designed for NextStep and then OpenStep compatibility, I've heard they are now more-or-less Cocoa compatible, but I've not played with any of it in almost 2 decades. Of course that only gets you as far as ObjC, not Swift, and I don't know if Apple is going to OpenSource it.

The low-level toolchain for Xcode (the gcc compiler family, the gdb debugger, etc.) is all open source and common to Unix and Linux platforms. But the IDE--the editor, project management, indexing, navigation, build system, graphical debugger, visual data modeling, SCM system, refactoring, project snapshots, etc.--is a Mac OS X Cocoa application, and is not portable.

Nobody suggested Vagrant yet, so here it is, Vagrant box for OSX

vagrant init https://vagrant-osx.nyc3.digitaloceanspaces.com/osx-sierra-0.3.1.box
vagrant up

and you have a MACOS virtual machine. But according to Apple's EULA, you still need to run it on MacOS hardware :D But anywhere, here's one to all of you geeks who wiped MacOS and installed Ubuntu :D

Unfortunately, you can't run the editors from inside using SSH X-forwarding option.