I also received this Google notification for a site and this was very confusing as I'm using Yoast for this particular site but breadcrumbs were not enabled there.

After checking the theme's customizer settings I found out that I had enabled an option there that adds Yoast's breadcrumbs in pages.
When I first did this I thought that I was enabling only breadcrumbs in my pages and that had nothing to do with SEO, hence not enabling them at Yoast settings.

Those breacrumbs work fine in all my site's pages and I'm still confused about the relation with Google and SEO. I really don't care if Google uses breadcrumbs at search results pages, all I want is having them displaying at my pages.

I finally enabled them also at Yoast settings and marked those notifications at Search Console as fixed in order to check if that solves the issue but it would be very helpful for someone to clarify what is the relation between Google breadcrumbs and those used by themes for displaying on top of pages for visitor's convenience as I can't see any.