Since the vast majority of Swift and SwiftUI documentation online is outdated, I've found that concatenating the best of "what's new in Swift 5.x / 6.x" blogs then asking it to organize that into a prompt for itself, then adding that to the system prompt, helps the LLM produce idiomatic and current code.

While these changes may require "new ways of thinking" in humans, the LLM seems to have these conceptual approaches embedded already thanks to other languages that did these things earlier. The what's new just shows it the syntax for these concepts in Swift.