Comment 0 for bug 1885743

In firefox 78.0, the browser.search.modernConfig setting defaults to true, and as a result the custom definitions installed in /usr/lib/firefox/distribution/searchplugins/locale/ by langpacks are not loaded.

The upstream meta-bug that tracks this new modern search engine configuration is https://bugzilla.mozilla.org/show_bug.cgi?id=1542235.

The setting can be reverted back to false for the 78.0 builds, but eventually the setting will go away (https://bugzilla.mozilla.org/show_bug.cgi?id=1619926), so the custom definitions need to be updated.

Relevant upstream documentation: https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/search/docs/SearchEngineConfiguration.rst