How do I open a new instance of an application by default in GNOME?

Also answered here: How to open new window instead of already open window in gnome

You can configure this globally with a tweak extension.

You can press super , write tweak , open tweak tools.

Then go to "extensions" and enable "launch new instance"

Example:

Click HERE to see an example


you can open new instance by pressing CNTRL + ENTER