I log into wayland session but only got blank screen, I have krunner (Alt+F2), but no Plasma Shell.
After installing kwin-wayland-backend-x11, it works fine, I think it should only need kwin-wayland-backend-drm.
I use Intel graphics, neon devunstable, 10-9-2016.
This is .wayland-errors for a failed session

startplasmacompositor: Starting up...
dbus-update-activation-environment: warning: error sending to systemd: org.freedesktop.DBus.Error.Spawn.ChildExited: Process org.freedesktop.systemd1 exited with status 1
No backend specified through command line argument, trying auto resolution
_XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
glamor: EGL version 1.4 (DRI2):
Configuring Lock Action
Session path: "/org/freedesktop/login1/session/_37"
QObject::connect: invalid null parameter
QObject::connect: invalid null parameter
Using Wayland-EGL
Loading stage  "initial" 23
Loading stage  "wm" 23
startplasma: Starting up...
QObject::connect: invalid null parameter
Config timer connecting...
Setting the name of  0x198eb80  to  "org.kde.ActivityManager.RunApplication"
Setting the name of  0x197b910  to  "org.kde.ActivityManager.ActivityTemplates"
Setting the name of  0x198ab50  to  "org.kde.ActivityManager.Resources.Scoring"
Creating directory:  "/home/mustafa/.local/share/kactivitymanagerd/resources/"
KActivities: Database connection:  "kactivities_db_resources_139872964204736_readwrite" 
    query_only:          QVariant(qlonglong, 0) 
    journal_mode:        QVariant(QString, "wal") 
    wal_autocheckpoint:  QVariant(qlonglong, 100) 
    synchronous:         QVariant(qlonglong, 1)
Cleaning up...
kdeinit5: preparing to launch '/usr/lib/x86_64-linux-gnu/libexec/kf5/klauncher'
kdeinit5: Launched KLauncher, pid = 4341, result = 0
QObject::connect: invalid null parameter
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
kdeinit5: opened connection to :1
kdeinit5: preparing to launch 'libkdeinit5_kded5'
kdeinit5: Launched KDED, pid = 4343 result = 0
kdeinit5: preparing to launch 'libkdeinit5_kcminit_startup'
kdeinit5: Launched 'kcminit_startup', pid = 4344 result = 0
QObject::connect: invalid null parameter
QObject::connect: invalid null parameter
kdeinit5: Got SETENV 'KDE_MULTIHEAD=false' from launcher.
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/keyboard.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/khotkeys.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/kscreen.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/networkwatcher.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/soliduiserver.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/kwrited.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/recentdocumentsnotifier.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/networkstatus.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/solidautoeject.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/proxyscout.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/remotedirnotify.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/baloosearchmodule.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/bluedevil.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/desktopnotifier.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/networkmanagement.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/ktimezoned.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/freespacenotifier.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/appmenu.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/device_automounter.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/ksysguard.so"
kf5.kded: No X-KDE-DBus-ServiceName found in "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kded/statusnotifierwatcher.so"
Initializing  "kcm_style" :  "kcminit_style"
kdeinit5: Got SETENV 'GTK_RC_FILES=/etc/gtk/gtkrc:/home/mustafa/.gtkrc:/home/mustafa/.config/gtkrc' from launcher.
kdeinit5: Got SETENV 'GTK2_RC_FILES=/etc/gtk-2.0/gtkrc:/home/mustafa/.gtkrc-2.0:/home/mustafa/.config/gtkrc-2.0' from launcher.
Initializing  "kded_touchpad" :  "kcminit_touchpad"
Initializing  "kcm_kgamma" :  "kcminit_kgamma"
Initializing  "kcm_input" :  "kcminit_mouse"
kdeinit5(4345) : KDE detected X Error: BadWindow (invalid Window parameter) 3
         Major opcode: 2
         Minor opcode: 0
         Resource id:  0x0
Initializing  "kcm_access" :  "kcminit_access"
kdeinit5: Got EXEC_NEW '/usr/bin/kaccess' from launcher.
kdeinit5: preparing to launch '/usr/bin/kaccess'
kf5.kded: found kded module "printmanager" by prepending 'kded_' to the library path, please fix your metadata.
kdeinit5: Got EXEC_NEW '/usr/lib/x86_64-linux-gnu/libexec/kf5/kconf_update' from launcher.
kdeinit5: preparing to launch '/usr/lib/x86_64-linux-gnu/libexec/kf5/kconf_update'
kdeinit5: PID 4344 terminated.
kdeinit5: PID 4353 terminated.
pm.kded: unable to register service to dbus
kdeinit5: PID 4352 terminated.
kf5.kcoreaddons.kaboutdata: Could not initialize the equivalent properties of Q*Application: no instance (yet) existing.
kdeinit5: Got KWRAPPER '/usr/bin/ksmserver' from wrapper.
kdeinit5: preparing to launch '/usr/bin/ksmserver'
QObject::connect: invalid null parameter
Qt: Session management error: networkIdsList argument is NULL
ksmserver: "/run/user/1000/KSMserver"
ksmserver: KSMServer: SetAProc_loc: conn  0 , prot= local , file= @/tmp/.ICE-unix/4361
ksmserver: KSMServer: SetAProc_loc: conn  1 , prot= unix , file= /tmp/.ICE-unix/4361
kdeinit5: Got SETENV 'SESSION_MANAGER=local/mustafa-All-Series:@/tmp/.ICE-unix/4361,unix/mustafa-All-Series:/tmp/.ICE-unix/4361' from launcher.
ksmserver: KSMServer::restoreSession  "saved at previous logout"
ksmserver: Starting autostart service  "/etc/xdg/autostart/baloo_file.desktop"
ksmserver: Starting autostart service  "/etc/xdg/autostart/krunner.desktop"
ksmserver: Starting autostart service  "/etc/xdg/autostart/pam_kwallet_init.desktop"
ksmserver: Starting autostart service  "/etc/xdg/autostart/plasmashell.desktop"
ksmserver: Starting autostart service  "/etc/xdg/autostart/polkit-kde-authentication-agent-1.desktop"
ksmserver: Starting autostart service  "/etc/xdg/autostart/xembedsniproxy.desktop"
ksmserver: Autostart 0 done
kcminit not running? If we are running with mobile profile or in another platform other than X11 this is normal.
ksmserver: Kcminit phase 1 done
ksmserver: Starting autostart service  "/etc/xdg/autostart/pulseaudio.desktop"
ksmserver: Autostart 1 done
Registering "org.kde.StatusNotifierItem-4273-1/StatusNotifierItem" to system tray
kscreen.kwayland: Loading Wayland backend.
Trying to convert empty KLocalizedString to QString.
Trying to convert empty KLocalizedString to QString.
Trying to convert empty KLocalizedString to QString.
Installing the delayed initialization callback.
bluedevil: Created
Using Wayland-EGL
kf5.kded: found kded module "touchpad" by prepending 'kded_' to the library path, please fix your metadata.
Delayed initialization.
Reloading the khotkeys configuration
ksmserver: Starting notification thread
ksmserver: Starting autostart service  "/etc/xdg/autostart/at-spi-dbus-bus.desktop"
Version 2 File!
ksmserver: Starting autostart service  "/etc/xdg/autostart/powerdevil.desktop"
true
Imported file "/usr/share/khotkeys/defaults.khotkeys"
Imported file "/usr/share/khotkeys/konqueror_gestures_kde321.khotkeys"
Imported file "/usr/share/khotkeys/kde32b1.khotkeys"
Imported file "/usr/share/khotkeys/spectacle.khotkeys"
ksmserver: Autostart 2 done
ksmserver: Kcminit phase 2 done
bluedevil: Bluetooth operational changed false
bluedevil: ObexManager operational changed false
kscreen.kded: Config KScreen::Config(0x211d220) is ready
kscreen.kded: PowerDevil SuspendSession action not available!
kscreen.kded: "The name org.kde.Solid.PowerManagement was not provided by any .service files"
kscreen.kded: Applying config
kscreen.kded: Applying ideal config
kscreen.kded: Connected outputs:  1
kscreen.kded: doApplyConfig()
kscreen.kwayland: Loading Wayland backend.
kscreen.kded: Config applied
kscreen.kded: Monitor for changes:  true
ksmserver: autostart service "plasmashell" finished with exit code  1
ksmserver: autostart service "start-pulseaudio-x11" finished with exit code  0
ksmserver: autostart service "/lib/x86_64-linux-gnu/libexec/pam_kwallet_init" finished with exit code  0
bluedevil: ObexManager operational changed true
bluedevil: ObexAgent registered
BluezQt: PendingCall Error: "Failed to activate service 'org.bluez': timed out"
()
("/home/mustafa/logs/freenode.log")
()
Creating the cache for:  "applications:org.kde.konversation.desktop"
Already in database?  true
      First update :  QDateTime(2016-09-10 12:57:16.000 AST Qt::TimeSpec(LocalTime))
       Last update :  QDateTime(2016-09-10 13:23:19.000 AST Qt::TimeSpec(LocalTime))
After the adjustment
     Current score :  2
      First update :  QDateTime(2016-09-10 12:57:16.000 AST Qt::TimeSpec(LocalTime))
       Last update :  QDateTime(2016-09-10 13:23:19.000 AST Qt::TimeSpec(LocalTime))
Interval length is  0
         New score :  3
This plugin does not support raise()
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete, missing attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete attachment.
QOpenGLFramebufferObject: Framebuffer incomplete, missing attachment.
org.kde.kwindowsystem.keyserver.x11: X11 implementation of KKeyServer accessed from non-X11 platform! This is an application bug.
Creating the cache for:  "applications:firefox.desktop"
Already in database?  true
      First update :  QDateTime(2016-09-10 11:03:13.000 AST Qt::TimeSpec(LocalTime))
       Last update :  QDateTime(2016-09-10 13:24:02.000 AST Qt::TimeSpec(LocalTime))
After the adjustment
     Current score :  2
      First update :  QDateTime(2016-09-10 11:03:13.000 AST Qt::TimeSpec(LocalTime))
       Last update :  QDateTime(2016-09-10 13:24:02.000 AST Qt::TimeSpec(LocalTime))
Interval length is  0
         New score :  3
This plugin does not support raise()
This plugin does not support raise()
This plugin does not support raise()
()
("/home/mustafa/logs/freenode_#kde-neon.log")
()
This plugin does not support raise()
This plugin does not support raise()
kdeinit5: Got EXEC_NEW '/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/file.so' from launcher.
kdeinit5: preparing to launch '/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/file.so'
kdeinit5: Got EXEC_NEW '/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/trash.so' from launcher.
kdeinit5: preparing to launch '/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/trash.so'
initialization OK, home trash dir: "/home/mustafa/.local/share/Trash"
listdir:  QUrl("trash:/")
kdeinit5: Got EXEC_NEW '/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/file.so' from launcher.
kdeinit5: preparing to launch '/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/file.so'
Creating the cache for:  "applications:org.kde.dolphin.desktop"
Already in database?  true
      First update :  QDateTime(2016-09-10 11:02:47.000 AST Qt::TimeSpec(LocalTime))
       Last update :  QDateTime(2016-09-10 12:24:07.000 AST Qt::TimeSpec(LocalTime))
After the adjustment
     Current score :  1
      First update :  QDateTime(2016-09-10 11:02:47.000 AST Qt::TimeSpec(LocalTime))
       Last update :  QDateTime(2016-09-10 12:24:07.000 AST Qt::TimeSpec(LocalTime))
Interval length is  0
         New score :  2
kdeinit5: Got EXEC_NEW '/usr/bin/kate' from launcher.
kdeinit5: preparing to launch '/usr/bin/kate'
QObject::connect: invalid null parameter
Using Wayland-EGL

Reproducible: Always