In addition I had to uninstall an older libinput package that had been installed as a dependency to vlc I think.
Now I got thumb support and multi-touch support out of the box, and the pointer doesn't jump around on the screen any more when I'm typing. Hopefully others will find this helpful.
After struggling with this for a long time I found out that there is a "new" driver for input devices: libinput, that replaces synaptics. I followed the install instructions as given here: http:// askubuntu. com/questions/ 649103/ proper- touchpad- thumb-palm- detection- with-libinput
In addition I had to uninstall an older libinput package that had been installed as a dependency to vlc I think.
Now I got thumb support and multi-touch support out of the box, and the pointer doesn't jump around on the screen any more when I'm typing. Hopefully others will find this helpful.