Quoting Seth ([Kicad-developers] Update to Footprint/Symbol paths):
Previously, KiCad had default paths for schematic symbols in
/usr/share/kicad/libraryand for footprints in/usr/share/kicad/modules/(Windows users found these at %{KICAD_PROGRAM}\share\kicad\library and %{KICAD_PROGRAM}\share\kicad\modules)Starting with tomorrow’s nightly build, we will be installing these to
/usr/share/kicad/symbolsfor schematic symbols and/usr/share/kicad/footprintsfor layout footprints.
Depending on your setup, this may require some manual intervention after an update. New installations should work by default.