Hello,
I recently started exploring the Swift programming language and found it very interesting, which motivated me to look into contributing to the Swift organization for GSOC’ 26.
Before proceeding further, I wanted to clarify one thing: is a macOS system (MacBook) required to contribute to Swift projects, or are there parts of the ecosystem where contributions can be made using other operating systems like Linux?
Currently, Windows, Linux, and macOS are supported host platforms. You should be able to work on any of those for the most part, though there are certainly times where it can be helpful to explicitly use a particular host if you are running into a platform specific issue. If you are looking at the broader ecosystem, you might even need a WASI, Android, or FreeBSD environment. It really depends on what you are working on and what hurdles you encounter along the way 
Thank you for clarifying. Looking forward to contributing to this organization !
If it helps, I've written, tested, and pushed code to the Swift Testing repo from macOS 26, Windows 11, Ubuntu 24, FreeBSD 14.3, and even OpenBSD 7.7. 
Yes, Thank you!
To that list, I'd like to add that I'm one of the top 100 committers to the Swift compiler repo and that was all done from my Android phone in the Termux app, with some stuff additionally done in a small linux VPS I rented remotely for testing on linux also, ie I did not have access to macOS locally till last month, but I was contributing for seven years before that. I would simply run my changes through the public macOS and Windows CI to make sure nothing broke on those OS platforms I had no access to, which is what most Swift devs have to do for some of the CI platforms.
So Swift is very much a cross-platform language, just follow the instructions on your preferred OS to get going.
respect++
Be sure to have plenty of RAM.