add 0209: geo.security.allowinsecure

mozilla intend to flip the switch in 55, but the pref is available in FF54 (but no idea if its fully working) - see https://webcache.googleusercontent.com/search?q=cache:yfO0BMezyGcJ:https://groups.google.com/d/msg/mozilla.dev.platform/8BsF76gNhDE/XhsZXcueBAAJ+&cd=2&hl=en&ct=clnk&gl=nz

user.js

@@ -89,6 +89,10 @@ user_pref("intl.accept_languages", "en-US, en");
 /* 0208: enforce US English locale regardless of the system locale
  * [1] https://bugzilla.mozilla.org/show_bug.cgi?id=867501 ***/
 user_pref("javascript.use_us_english_locale", true); // (hidden pref)
+/* 0209: disable geolocation on non-secure origins (FF55+)
+ * [1] https://bugzilla.mozilla.org/show_bug.cgi?id=1072859
+ * [2] https://www.ghacks.net/2017/03/14/firefox-55-geolocation-requires-secure-origin/ ***/
+user_pref("geo.security.allowinsecure", false");
 
 /*** 0300: QUIET FOX [PART 1]
      No auto-phoning home for anything. You can still do manual updates. It is still important