laney@nightingale> ls /usr/share/ubuntu/applications/mimeinfo.cache                                                                                                    /usr/share/ubuntu/applications
ls: cannot access '/usr/share/ubuntu/applications/mimeinfo.cache': No such file or directory
laney@nightingale> python3 -c 'from gi.repository import Gio; print(Gio.DesktopAppInfo.get_default_for_uri_scheme("appstream").get_id())'                              /usr/share/ubuntu/applications
Traceback (most recent call last):
  File "<string>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'get_id'
laney@nightingale> sudo env XDG_DATA_DIRS=${XDG_DATA_DIRS} update-desktop-database -q                                                                                  /usr/share/ubuntu/applications
laney@nightingale> ls /usr/share/ubuntu/applications/mimeinfo.cache                                                                                                    /usr/share/ubuntu/applications
/usr/share/ubuntu/applications/mimeinfo.cache
laney@nightingale> python3 -c 'from gi.repository import Gio; print(Gio.DesktopAppInfo.get_default_for_uri_scheme("appstream").get_id())'                              /usr/share/ubuntu/applications
org.gnome.Software.desktop