real-vnc-server funktioniert nicht, in raspi-config VNC abschalten
see https://www.raspberrypi.org/forums/viewtopic.php?f=66&t=122007

installiert:
sudo apt-get install vino dconf-editor

type:
dconf-editor
This opens a window on your laptop with dconf-editor
go to:
org ==> gnome ==> desktop ==>remote-access
uncheck prompt-enabled
uncheck require-encryption

close dconf-editor
(I opened dconf-editor again to check if everything was saved)


to start vino at boot type:
mkdir /home/pi/.config/autostart

nano /home/pi/.config/autostart/vino.desktop

Than copy / paste below into nano

[Desktop Entry]
Encoding=UTF-8
Type=Application
Name=VINO
Comment=
Exec=/usr/lib/vino/vino-server
StartupNotify=false
Terminal=false
Hidden=false

press the key combination (at the same time)
control X
confirm with Y
than enter

don't forget to reboot the pi, else it won't work. type:
sudo reboot

I think you also need to have run, raspi-config in the terminal to make sure you boot into a desktop with autologin. I already did that, so I can't check if that is really needed or not

I hope this helps !
(I use remmina to log in from the ubuntu laptop to the Pi)