Just for the record in case somebody else has the same problem.
If a template has been built with Elementor and you would like to replace the main background image on Home:
01- From Home
02- Click option “Edit Page” on top
03- Once inside the page, then click “Edit with Elementor”
04- Go to “General settings”, there you will find the option to replace the image.
Note: If at first sight after clicking “Edit with Elementor” you cannot see the “General settings” option for the page, look at the bottom left, there will be a small screw type of symbol, there you will find them.