[adrianhall]

Summary

Chooses a deliberate minimum iOS and Android version for the mobile sample apps, aligns them across the MAUI, Avalonia and Uno samples, and documents the values and the tooling needed to build them.

Closes #628

Final values

Sample	iOS	Android	Windows
MAUI	15.0 -> 18.0	21.0 -> 24.0	10.0.17763.0 (unchanged)
Avalonia	15.0 -> 18.0 (csproj and Info.plist)	34 -> 24	n/a
Uno	not set -> 18.0 (also Mac Catalyst 18.0)	not set -> 24.0	n/a

Rationale

• iOS 18.0. Avalonia 12 treats iOS 26 as Tier 1, iOS 18.x as Tier 2, and iOS 17 and earlier as Tier 3. MAUI 10 supports iOS 12.2+ and Uno defaults to 14.2 (6.x) / 15.0 (7.0), so 18.0 sits inside every framework's supported range. The Datasync client library has no iOS-specific API requirements, so it does not constrain the choice. The samples should reflect what a new app would reasonably choose today. Mac Catalyst uses the iOS-equivalent number (18.0 = macOS 15).
• Android API 24. .NET 11 raises the MAUI minimum to API 24, Uno 7.0 uses API 24 on both net10.0-android and net11.0-android, and MAUI Blazor Hybrid already requires it. It also removes the odd difference between MAUI (21) and Avalonia (34).
• Windows unchanged. 10.0.17763.0 is the Windows App SDK floor and is already the value used by the WinUI3 sample, so there is no reason for it to differ.
• Avalonia Info.plist and csproj agree (both 18.0).
• Uno now sets the values explicitly so the target is visible in the project instead of depending on the Uno.Sdk default.
• UIRequiredDeviceCapabilities. Avalonia's iOS Info.plist listed armv7 (a 32-bit architecture that no iOS 18 device has) and the Uno iOS Info.plist listed both armv7 and arm64. Both now use arm64 only, which matches the MAUI sample.

Documentation

docs/samples/todoapp/{maui,avalonia,unoplatform}.md each gain a "Minimum OS versions and tooling" section listing the minimum versions and what is needed to build the mobile heads (Xcode 26.6 and workload set 10.0.112 for iOS, which is what CI pins; JDK 21 and the Android SDK with API 36 for Android).

Verification

• dotnet restore and dotnet build succeed locally (0 warnings, 0 errors). dotnet test could not run locally because only the .NET 11 runtime is installed on the author's machine; no library or test code changed.
• The mobile heads cannot be built locally. They are validated by the Build Samples workflow, in particular todoapp-maui / ios, todoapp-avalonia / ios and todoapp-uno / ios-maccatalyst.

Follow-ups

• Samples: remove Mac Catalyst from the Uno sample (unsupported in Uno Platform 7.0) #632: remove Mac Catalyst from the Uno sample (unsupported in Uno Platform 7.0), including CI and docs. The Mac Catalyst rows added to unoplatform.md here should be removed as part of that work.
• Infra: drop the 10.0.107 workload set pin and move iOS/Mac Catalyst sample CI to Xcode 26.5+ #627: drop the workload set pin and move to Xcode 27 (the Xcode and workload versions in the docs should be updated with it).