It has been used to build and and submit an app on a Linux machine, according to: https://x.com/JoshuaSWarren/status/2109068298537066710

This directly challenges the author's claim "You can't build iOS apps without a Mac."

omarchy-apple-dev is built on: https://xtool.sh which is "a cross-platform (Linux/WSL/macOS) tool that replicates Xcode functionality with open standards."

There's also: https://github.com/MarcoDotIO/Ycode - which even includes an experimental simulator.