To force the burger to always open when users access the page, you can use this CSS code to Website > Website Tools > Custom CSS.
body:not(.header--menu-open) .header-menu {
opacity: 1 !important;
visibility: visible !important;
}
body.header--menu-open .header-menu {
opacity: 0 !important;
visibility: hidden !important;
}
To make this appears on Homepage Only, use this new CSS code
body.homepage:not(.header--menu-open) .header-menu {
opacity: 1 !important;
visibility: visible !important;
}
body.homepage.header--menu-open .header-menu {
opacity: 0 !important;
visibility: hidden !important;
}