Global:
/*** Take out the divider line between content and sidebar ***/
#main-content .container:before {background: none;}
/*** Expand the content area to fullwidth ***/
@media (min-width: 981px){
#left-area {
width: 100%;
padding: 23px 0px 0px !important;
float: none !important;
}
}
https://www.elegantthemes.com/blog/divi-resources/how-to-remove-sidebars-from-divi