I tried to solve my problem that my touchpad is not running on my Lenovo 720-15IKB by installing the latest rc kernel 4.14.rc5 as described here, which really worked! The touchpad is working then! But now I have a new problem caused by that kernel:
Networking doesn't work correctly with kernel 4.14-rc5
I don't get any IPv4 IP any more in my local Network. IPv6 works correctly. If IPv6 is running in your network, You could add all needed addresses by hand in my /etc/hosts file, but that is no solution ;)
I could only workaround it like this:
Instead of DHCP I used manual wifi configuration which still didn't help at first. Then I connected a USB-LAN adapter once and noticed, that I got a correct internet settings via LAN then. This seems somehow to have fixed some misconfiguration. I can now get correct internet settings via WiFi too. Also after a reboot I can reconnect via WiFi only. But DHCP still doesn't work. I tested this with 3 different WiFis in different places.
I just installed plain standard Ubuntu 17.10 with systemd and Network Manager, no modifications.
How can I get IP4 with DHCP running with the latest kernel?