causes the home page AboutHome not to completely load the search engine and not to initialize "session restore". No information is added in the console.
Things changed after importing newtab. Session restore is not correctly initialized (needs a refresh) independently from these observers, so they have been added.
From old project
In TelemetryEnvironment.jsm, this observer addition:
Services.obs.addObserver(this, SEARCH_SERVICE_TOPIC, false);
causes the home page AboutHome not to completely load the search engine and not to initialize "session restore". No information is added in the console.