Xcode 26.4 breaks compilation: Sending 'activity' risks causing data races

After updating Xcode and SDK to 26.4, I'm now getting an concurrency error when trying to update or end live activities with the following code that built successfully before:

        // Get list of active activities
        let allActivities = Activity<ArbeitszeitWidgetAttributes>.activities
        
        // Cancel all active activities
        Task {
            for activity in allActivities {
                await activity.end(nil, dismissalPolicy: .immediate)
            }
        }

Sending 'activity' risks causing data races.

Sending main actor-isolated 'activity' to @concurrent instance method 'update' risks causing data races between @concurrent and main actor-isolated uses

I'm currently using

nonisolated(unsafe) let activity = activity
await activity.end(nil, dismissalPolicy: .immediate)

to get it to compile again. What's the best approach here?