We've long known that rel= "canonical" is not a directive. Even to eliminate internal duplicate content, Google will decide which page to index and rank based on internal links and other signals (such as content depth and relevancy).
In general, when you syndicate or republish your content across platforms, you're trading the extra visibility within that platform with the possibility that the other platform will appear in the search results above your website... ...the rel=canonical is not a directive, even within the same site.
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