This is the same bug at Ubuntu; it has more analysis: https://bugs.launchpad.net/ubuntu/+source/pepperflashplugin-nonfree/+bug/1632870
In short: * Google Chrome 54+ does not bundle libpepflashplayer.so. * pepperflashplugin-nonfree will have to get it from somewhere else; either adobe.com directly, or Google's "redirector.gvtl.com" thing. It looks like Ubuntu don't care about pepperflashplugin-nonfree, because they recommend adobe-flashplugin from canonical-partners. https://wiki.ubuntu.com/Chromium/Getting-Flash Debian has no equivalent.