Following some tutorials will produce a 500 internal server error.

This post only uses CSS to remove the sidebar from bbPress when using the Divi theme.

Simply add the following CSS to your Divi > Theme Options > Custom CSS:

.bbpress #sidebar {display: none;}
@media only screen and (min-width: 981px) {
.bbpress #main-content .container:before {display: none;}
.bbpress #left-area {width: 100%;}
.bbpress.et_right_sidebar #left-area {
float: none;
padding-right: 0;
}
}