Swift 6 is only painful if you wrote a ton of terrible Swift 5, and even then Swift 5 has had modes where you could gracefully adopt the Swift 6 safety mechanisms for a long time (years?)

~130k LoC Swift app was converted from 5 -> 6 for us in about 3 days.

Yes and no, our app is considerably larger than 130k LoC. While we’ve migrated some modules there are some parts that do a lot of multithreaded work that we probably will never migrate because they’d need to essentially be rewritten and the tradeoff isn’t really worth it for us.

It's also painful if you wrote good Swift 5 code but now suddenly you need to closely follow Apple's progress on porting their own frameworks, filling your code base with #if and control flow just to make the compiler happy.