The above javascript fix won't work for the start page, when it is also linked to by the header logo, as in my case, using the sprintDoc template. I actually wanted to tweak that, to have a nice entry of my start page in my sitemap.
However, if you want to have a Breadcrumb independent from your page heading, you can just place an extra <h1> heading in front of your actual <h1> page heading. Now, all you need to do is to hide that first (extra) heading!
Example given, assuming that your hidden (extra) heading is ====== Start Page ====== :
div.dokuwiki h1#start_page { display: none; } // hide heading
Place the above line into /dokuwiki/conf/userall.css (Create if it does not exist!)
And, as always, save your file, don't forget to clear the cache in your dokuwiki\data\cache and refresh or restart your browser!
Now, the hidden heading is not shown on the page, but, used by breadcrumbs and sitemap when "useheading" is activated.