Joy
(@joyously)
Themes sometimes have to override the nav walker class to get the HTML output that they need for the menu. There are a couple of filters in there, if they do what you want then add a filter and you’re done. If not, you can override the class and change it up.
https://developer.ww.wp.xz.cn/reference/classes/walker_nav_menu/
Menus are the tricky part of a theme, so while there are thousands of themes in the repository you can look at (to see how they do it), it’s unlikely that a theme author will walk it through with you here.