Swift value(forKeyPath keyPath: String) not available at Linux

Question

My main goal is to extract from a JSON file a value or an array of values identified by a keyPath. On macOS I have created the following method for this.

extension JSONDecoder
{
    func decode<T: Decodable>(_ type: T.Type, from data: Data, keyPath: String) throws -> T
    {
        // Create Foundation object for the entire JSON data
        let toplevel = try JSONSerialization.jsonObject(with: data)
        
        // Extract part identified by the given keyPath
        if let nestedJson = (toplevel as AnyObject).value(forKeyPath: keyPath)
        {
            // Create a data-object from that part
            let nestedJsonData = try JSONSerialization.data(withJSONObject: nestedJson)
            // Try to create an object of the given type from the data-object
            return try decode(type, from: nestedJsonData)
        }
        else
        {
            throw DecodingError.dataCorrupted(.init(codingPath: [], debugDescription: "Nested json not found for key path \"\(keyPath)\""))
        }
    }
}

For example, this allows me to extract an array of strings with the keyPath [email protected] by doing something like

if let categories = try JSONDecoder().decode([String].self, from: data, keyPath: keyPath)
{
}

Unfortunately the function func value(forKeyPath keyPath: String) -> Any? is not available under Linux and I am now looking for an alternative.