Combine PassthroughSubject is not Sendable

Using Swift
1

Hi, I usually have a singleton that contains a Combine's publisher like this:

import Combine
struct TestSingleton: Sendable {
    static let shared = TestSingleton()
    private init() {}
    
    let publisher = PassthroughSubject<Void, Never>() 
}

Swift 6 complete concurrency check will give me a compiler warning: Stored property 'publisher' of 'Sendable'-conforming struct 'TestSingleton' has non-sendable type 'PassthroughSubject<Void, Never>'

It seems like the PassthroughSubject is non-sendable. How should I deal with this? The compiler suggests adding @preconcurrency to the Combine the import module line.

@preconcurrency import Combine

That silences the compiler error.

Question: Should I add that @preconcurrency label? Another way is to add @MainActor to the struct, but I'm unsure if I want this to be on the main thread. For context, the publisher here will emit a signal when the user clicks something on the UI.