Hi Michael,

Yes, PowerServer 2021 and newer only support Windows OS.  We just didn't see a lot of demand to run PB apps on iOS/Android, and at the same time if we only ran on Windows OS we could support nearly 100% of PB features.  It was not a decision we took lightly, but its hard not to prioritize majority of customers' needs.

In terms of wind-down transition plan on iOS/Android, we have designated PowerServer 2020 as a long-term support (LTS) version to give customers adequate time to migrate off this feature.  This version will be supported until January 22, 2026.  So aside from being able to get technical support, we plan to keep releasing updates for newer iOS/Android versions.

But there are three important points to remind you:

1. Supporting newer iOS/Android versions will always require an update of PowerServer.  So the answer is no, your existing build is not going to work for iOS 15.  You will need an update from Appeon.

2. It has always been the case ever since we first added the iOS/Android feature to PowerServer back in 2016 that it trails the OS releases.  We typically support newer iOS versions few months after they are released.  Please contact our product management team at product@appeon.com to get an estimated date for iOS 15 support.

3. For quite some time now, we no longer post updated workspaces to the Apple app store.  Apple's policies have become so ridiculous and constantly changing that it just doesn't make sense anymore given small user base we have deploying through app store. So you will need to compile and distribute the workspace yourself (rather than through app store).

In terms of migration, our recommended path is you use the PowerScript Migrator (that is included with your PB subscription) to migrate your mobile app's business logic to C# REST APIs and then develop a new UI.  Since they are REST APIs you can use whatever UI you like.  

Best regards,
Armeen