Hello
Is it possible to add mutliple popups on the map without an extension ?
There is only one popup per View. If you want to try and simulate showing multiple popups, you can use the Feature widget, which displays Popup content and have multiple Feature widgets in your application.
Here is a sample showing multiple Feature widgets in a side panel.
https://developers.arcgis.com/javascript/latest/sample-code/widgets-feature-multiplelayers/