I have the following code. It simply run Vision API to get the text from the image. I use very simple GCD to dispatch the heavy Vision operation to the background queue, and then dispatch it back to main queue for completion:

public struct TextRecognitionResult {
  let observation: VNRecognizedTextObservation
  let text: VNRecognizedText
  let rect: CGRect
}

public enum TextRecognitionUtil {
  
  private static let queue = DispatchQueue(label: "text_recognition", qos: .userInitiated)

  public static func process(
    image: UIImage,
    recognitionLevel: VNRequestTextRecognitionLevel,
    completion: @Sendable @escaping ([TextRecognitionResult]) -> Void)
  {
    guard let cgImage = image.cgImage else {
      completion([])
      return
    }
    let request = VNRecognizeTextRequest { (request, error) in
      guard
        error == nil,
        let observations = request.results as? [VNRecognizedTextObservation]
      else {
        DispatchQueue.main.async {
          completion([])
        }
        return
      }
      
      var results = [TextRecognitionResult]()
      
      // Vision's origin is on bottom left
      let transform = CGAffineTransform.identity
        .scaledBy(x: 1, y: -1)
        .translatedBy(x: 0, y: -image.size.height)
        .scaledBy(x: image.size.width, y: image.size.height)

      for observation in observations {
        guard let text = observation.topCandidates(1).first else { continue }
        let rect = observation.boundingBox.applying(transform)
        results += [TextRecognitionResult(observation: observation, text: text, rect: rect)]
      }
      DispatchQueue.main.async {
        completion(results)
      }
    }
    
    request.recognitionLevel = recognitionLevel
    self.queue.async {
      let handler = VNImageRequestHandler(cgImage: cgImage, options: [:])
      try? handler.perform([request])
    }
  }
}

This code violates Swift 6 concurrency, because TextRecognitionResult is not Sendable. The TextRecognitionResult can’t be Sendable, because VNRecognizedTextObservation and VNRecognizedText is not Sendable, and they are both types defined in Vision that I cannot change.