As far as I understand it, from reading the documentation for media9, videos are generally embedded in PDFs by including Flash video players in the PDF.
Unfortunately that means readers that can play video need to use Flash, which is long dead. I think the only reader (with maybe some minor exceptions) that supports it is Acrobat, and even then only on Windows.
So, is there a more modern way to embed videos in PDFs that doesn't rely on Flash, and do any common PDF viewers support it? If not, are there any plans to add this obviously useful feature?