Now that we've upgraded our own Moodle sites to 3.5 I am starting to take a look at some of the more finer details of the theme and this morning I applied some styling to the breadcrumbs. This is the same styling from our evolve-D theme but just made to work better with Boost.
The really nice part about this is they look great on desktop and when your screen drops down to phone size it automatically reverts back to the default Boost text such as Home / Coursename / activity .
Also, only breadcrumbs with links will be displayed. The text only items just seem to take up space and do nothing for the end user.