Headers with submenus could be a problem on displays with touchscreens, specially if the submenu parent has a link to a page or to an external source. This guide will help you in making submenus touchscreen-friendly.
In your custom CSS file, add @media (pointer: coarse) property. This media query targets all devices with touchscreen displays.

The code below enables the user to tap the submenu parent and show the submenus without being redirected to the page/external link.
/* for devices with touchscreens */
@media (pointer: coarse) {
/* for submenus */
header ul.wp-block-navigation__container > li.has-child > a{
pointer-events: none;
}
}
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