I remember that AutoHotKey connector is listed in integration service few days ago, because I know AutoHotKey name from there. However, it connot be found there now.
The package is only supporting legacy project for now as the message also saying the same. If you have any older project which is Windows Legacy type, you can use this package in it.
For Windows type of the project you can raise a service request with UiPath support team to get exact timelines when this will be available for Windows compatibility as well.
The UiPath.Script.Activity package is not compatible with the Windows framework because it was designed for the Windows Legacy framework.
You can switch your project to the Windows Legacy framework or, alternatively, use the Start Process activity to run AutoHotKey scripts externally by calling AutoHotkey.exe with the script path as an argument.