However, they can be restored…
First, edit the master page in SharePoint Designer or Design Manager. I’ve used Design Manager here, and I’ve found the section of the page about Breadcrumbs. You’ll notice that it’s hidden, and the breadcrumb control is hidden:
This is despite there being an image in the page, and an apparently valid URL to a valid image:
document.getElementById("GlobalBreadCrumbNavPopout-anchor").innerHTML='<img style="border-width:0;position:absolute;left:-215px !important;top:-120px !important;" alt="Navigate Up" src="/_catalogs/theme/Themed/79206BD5/spcommon-B35BB0A9.themedpng">';
And you should now get an up-icon:
You could, of course, use a different icon. It’s also worth noting that some work on the drop down menu itself may need a little work (each row is supposed to be indented from the one above).