Firefox-esr 60.5.0esr-1~deb9u1 tries to install Widevine 1.4.8.1008, but the installation fails.
Firefox 65 from mozilla.org installs Widevine 4.10.1196.0 in ~/.mozilla. This installation succeeds, and after that EME works. After that Firefox-esr 60.5.0esr-1~deb9u1 works too. I did not found a way to install Widevine 4.10.1196.0 with firefox-esr 60.5.0esr-1~deb9u1. -- Paul van der Vlis Linux systeembeheer Groningen https://www.vandervlis.nl/