Hi Sven & Kathryn, Sven, thanks for your workaround. FYI regarding "Does anyone know how to contact the admins of this service?" Someone reported the same issue to mozilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1524830 Apparently it is more than just the aus server pointing to the wrong widevine version, it is firefox that do not fetch esr version.
Thus another workaround was proposed in above bugzilla report: cd /usr/lib/firefox-esr/defaults/pref edit channel-prefs.js and change the line: pref("app.update.channel", "default"); to pref("app.update.channel", "esr"); then restart firefox. It worked for me: 60.5.0esr-1~deb9u1 then automatically gets widevine 4.10.1196.0 instead of 184.108.40.2068 Regards, Franck