You won’t have the Mendix frontend available from microflow in your published REST service so you can’t use a Show Page action to do this.
You do have the $HttpResponse object available in your microflow. What you can do is add a new HttpHeader object associated to the $HttpResponse. In the HttpHeader set the key to be “Location” and the value to be “/”. Return the $HttpResponse at the end of your microflow. When the browser sees the location header it should reload your application from the homepage. If you need it go to a deeplink just replace the “/” with the value of the deeplink.
https://docs.mendix.com/refguide/http-request-and-response-entities/
Hope this helps