diff -up firefox-81.0/toolkit/modules/GMPInstallManager.jsm.old firefox-81.0/toolkit/modules/GMPInstallManager.jsm
--- firefox-81.0/toolkit/modules/GMPInstallManager.jsm.old	2020-09-25 10:39:04.769458703 +0200
+++ firefox-81.0/toolkit/modules/GMPInstallManager.jsm	2020-09-25 10:39:22.038504747 +0200
@@ -54,10 +54,6 @@ function getScopedLogger(prefix) {
 
 const LOCAL_GMP_SOURCES = [
   {
-    id: "gmp-gmpopenh264",
-    src: "chrome://global/content/gmp-sources/openh264.json",
-  },
-  {
     id: "gmp-widevinecdm",
     src: "chrome://global/content/gmp-sources/widevinecdm.json",
   },