Google announced this morning that starting on July 1, 2019 they will begin to index new web sites, not yet discovered by Google, using mobile-first indexing by default. Old web sites not yet in mobile-first indexing still won't be switched until they are ready but brand new sites, not yet indexed by Google, will come right out of the gate as using mobile-first indexing....
-
Google To Index New Web Sites Using Mobile-First Indexing By Default
seroundtable.com