Apple churns languages every few years? They kept Objective-C around for 13 years before introducing Swift, and that was a language that was widely disliked by people from outside the Apple ecosystem. You can still use it for the vast majority of OS features today[0], nearly 20 years after it was first used on Apple platforms. Heck, Obj-C is used for Mac/iOS development because that was the preferred language for Mac OS X's immediate ancestor, NextSTEP, which means that it's been a part of the same development ecosystem for about 30 years. If this is churn, I think I'm okay with it.

[0] As far as I know, the only system feature that requires Swift is iOS 14/macOS 11's new widgets, which must be written in SwiftUI.

Next is not MacOS so I think it’s a real stretch to claim that means long term support! Perhaps some of this is normal but I think Apple have made little effort to avoid churn and it suits them to keep things changing.

Apple have had significant churn in dev tooling, languages, sdks, frameworks, chip architectures over the last couple of decades. Perhaps that is completely normal but it does mean developers are always struggling to keep up, and an app written for iOS 1.0 needs significant alterations if not a rewrite to work with later versions. Almost everything has been completely replaced, from language to frameworks to dev tooling like resources.

Although I agree with your post, I still remember the Object Pascal, C++ PowerPlant/Carbon and Java Bridge days.

Right... Because Apple has done that so many times... oh wait they have done it exactly once since re-launching after acquiring NeXT. IT was Obj-C and now it's Swift except they actively support Obj-C still, so I'm not sure what you are talking about?

Apparently you need to count better.

Java was introduced alongside Objective-C, with a common bridge to call into Objective-C runtime, as Apple was unsure if the Apple developer community would be welcoming to Objective-C.

They dropped it after the community was more than happy to adopt Objective-C.

About the same time they introduced PyObjC support and for a while there was MacRuby, which due to internal politics was eventually dropped, the creator left and now sells RubyMotion for mobile development, originally based on it.

Then if we switch back to the System days, there was Object Pascal, replaced by C++ frameworks, Hypercard, Lisp, Dylan.

Nice shifting of the goal posts. Introducing a possible technology while supporting your main one is hardly the same thing. Since Next became OS X Objective-C has been supported and it has been the main focus of development until Swift. Apple is a different company after Next, the System days have no real bearing on modern Apple. Java, PyObjC, and MacRuby were all attempts to offer more ways into the main eco-system. They were never attempts to support a new dev environment. Swift is the only time Apple has done that since Jobs returned.