Search engines may index page URLs with the 'pk_vid' cross domain URL parameter added, for example in these search results:
Could we maybe prevent this parameter from appearing in indexed URLs?
Not sure what would be the best solution for this for users, and whether there is even a simple solution... for example:
(then we might document what we did in the Cross domain FAQ: https://matomo.org/faq/how-to/faq_23654/)
Canonical URL be the way to go.