As recommended by the docs for
The returned source may actually consist of multiple schema sources from different directories, depending on which directories were given in XDG_DATA_DIRS and GSETTINGS_SCHEMA_DIR. For this reason, all lookups performed against the default source should probably be done recursively.
Now it's actually found and works again, including subpixel font smoothing.
Closes: gnome-shell#1447 (closed)