If anyone knows how to make the iPhone 18 Pro work with Xcode 26 on Sequoia, and in turn with iOS 27, I (and I'm sure many other people) would be very happy to hear how!
But it is possible to run even the latest Xcode 26.6 by directly executing Xcode.app/Contents/MacOS/Xcode, and Xcode will run. This trick doesn't work with Xcode 27 anymore though. If you try that, you'll see a warning message that says something like "Xcode requires macOS 26 to run".
I'm still running Leopard. The built in X11 server, combined with X11 forwarding, and a Linux box works fine for my meager needs. I can run Chromium using X11 forwarding, seems to work fine for the most part.