Ticket #45866: 45866.2.patch

src/wp-content/themes/twentynineteen/sass/navigation/_menu-main-navigation.scss

@@ -205 +205 @@
                                 line-height: $font__line-height-heading;
                                 text-shadow: none;
                                 padding: calc( .5 * #{$size__spacing-unit} ) calc( 24px + #{$size__spacing-unit} ) calc( .5 * #{$size__spacing-unit} ) $size__spacing-unit;
-                                white-space: nowrap;
+                                max-width: #{20 * $size__spacing-unit};
 
                                 &:hover,
                                 &:focus {

src/wp-content/themes/twentynineteen/style.css

@@ -2959 +2959 @@
   line-height: 1.2;
   text-shadow: none;
   padding: calc( .5 * 1rem) calc( 24px + 1rem) calc( .5 * 1rem) 1rem;
-  white-space: nowrap;
+  max-width: 20rem;
 }
 
 .main-navigation .sub-menu > li > a:hover, .main-navigation .sub-menu > li > a:focus,