diff -Nru ubiquity-20.04.15.5/debian/changelog ubiquity-20.04.15.6/debian/changelog
--- ubiquity-20.04.15.5/debian/changelog	2021-01-25 12:28:35.000000000 -0600
+++ ubiquity-20.04.15.6/debian/changelog	2021-01-27 15:40:31.000000000 -0600
@@ -1,3 +1,10 @@
+ubiquity (20.04.15.6) focal; urgency=medium
+
+  * Listen on systemd signals in order to wait for sound.target to come
+    up before attempting to play the system ready sound (LP: #1901043)
+
+ -- William 'jawn-smith' Wilson <william.wilson@canonical.com>  Wed, 27 Jan 2021 15:40:31 -0600
+
 ubiquity (20.04.15.5) focal; urgency=medium
 
   [ Mauricio Faria de Oliveira ]
diff -Nru ubiquity-20.04.15.5/ubiquity/frontend/gtk_ui.py ubiquity-20.04.15.6/ubiquity/frontend/gtk_ui.py
--- ubiquity-20.04.15.5/ubiquity/frontend/gtk_ui.py	2021-01-25 12:28:35.000000000 -0600
+++ ubiquity-20.04.15.6/ubiquity/frontend/gtk_ui.py	2021-01-27 15:40:31.000000000 -0600
@@ -402,13 +402,19 @@
             self.live_installer.connect(
                 'key-press-event', self.a11y_profile_keys)
 
+        # Wait for sound.target to become ready
+        self.soundWatcher = misc.SystemdUnitWatcher('sound.target',
+                                                    self.play_system_ready)
+
+        self.save_oem_metapackages_list()
+
+    def play_system_ready(self):
+        # play the system ready sound
         if osextras.find_on_path('canberra-gtk-play'):
             subprocess.Popen(
                 ['canberra-gtk-play', '--id=system-ready'],
                 preexec_fn=misc.drop_all_privileges)
 
-        self.save_oem_metapackages_list()
-
     def save_oem_metapackages_list(self, wait_finished=False):
         ''' If we can, update the apt indexes. Then run 'ubuntu-drivers
         list-oem' to find any OEM metapackages for this system. If we've
diff -Nru ubiquity-20.04.15.5/ubiquity/misc.py ubiquity-20.04.15.6/ubiquity/misc.py
--- ubiquity-20.04.15.5/ubiquity/misc.py	2021-01-25 12:28:35.000000000 -0600
+++ ubiquity-20.04.15.6/ubiquity/misc.py	2021-01-27 15:40:31.000000000 -0600
@@ -11,6 +11,7 @@
 import syslog
 
 from ubiquity import osextras
+from gi.repository import Gio, GLib, GObject
 
 
 def utf8(s, errors="strict"):
@@ -942,4 +943,97 @@
     subprocess.Popen(['sensible-browser', uri], close_fds=True,
                      preexec_fn=drop_all_privileges)
 
+
+class SystemdUnitWatcher:
+    def __init__(self, unit, cb):
+        # try connecting to the bus
+        try:
+            self.system_bus = Gio.bus_get_sync(Gio.BusType.SYSTEM)
+            self.system_bus.call_sync(
+                "org.freedesktop.systemd1",
+                "/org/freedesktop/systemd1",
+                "org.freedesktop.systemd1.Manager",
+                "Subscribe",
+                None,  # parameters
+                None,  # reply type
+                Gio.DBusCallFlags.NONE,
+                -1,  # timeout
+                None,  # cancellable
+            )
+            self.system_bus.call(
+                "org.freedesktop.systemd1",
+                "/org/freedesktop/systemd1",
+                "org.freedesktop.systemd1.Manager",
+                "LoadUnit",
+                GLib.Variant("(s)", (unit,)),  # parameters
+                GLib.VariantType("(o)"),  # reply type
+                Gio.DBusCallFlags.NONE,
+                -1,  # timeout
+                None,  # cancellable
+                self._on_get_unit,
+                cb,  # user_data
+            )
+            self.proxy = None
+            self.properties_changed_signal = None
+        except GLib.Error:
+            pass
+        except IOError:
+            pass
+
+    def stop(self):
+        if self.properties_changed_signal:
+            GObject.signal_handler_disconnect(
+                self.proxy, self.properties_changed_signal
+            )
+            self.properties_changed_signal = None
+        self.proxy = None
+
+    def _on_properties_changed(
+        self, proxy, changed_properties, invalidated_properties, cb
+    ):
+        try:
+            if changed_properties["ActiveState"] == "active":
+                self.stop()
+                cb()
+        except KeyError:  # this property didn't change
+            pass
+
+    def _on_got_unit_proxy(self, conn, res, cb):
+        self.proxy = conn.new_finish(res)
+        self.properties_changed_signal = self.proxy.connect(
+            "g-properties-changed", self._on_properties_changed, cb
+        )
+        active_state = self.proxy.get_cached_property(
+            "ActiveState"
+        ).get_string()
+        if active_state == "active":
+            self.stop()
+            cb()
+
+    def _on_get_unit(self, conn, res, cb):
+        try:
+            object_path_v = conn.call_finish(res)
+            object_path = object_path_v.get_child_value(0).get_string()
+            Gio.DBusProxy.new(
+                conn,
+                Gio.DBusProxyFlags.GET_INVALIDATED_PROPERTIES,
+                None,  # GDBusInterfaceInfo
+                "org.freedesktop.systemd1",
+                object_path,
+                "org.freedesktop.systemd1.Unit",
+                None,  # cancellable
+                self._on_got_unit_proxy,
+                cb,  # user_data
+            )
+        except GLib.Error as e:
+            if (
+                e.matches(Gio.io_error_quark(), Gio.IOErrorEnum.DBUS_ERROR) and
+                Gio.DBusError.get_remote_error(e) ==
+                "org.freedesktop.systemd1.NoSuchUnit"
+            ):
+                pass  # the unit doesn't exist, tweak this to error if desired
+            else:
+                raise
+
+
 # vim:ai:et:sts=4:tw=80:sw=4: