Comment 4 for bug 1722478

Sigh, and it broke again after this morning's updates and a reboot. Here is a list of the updates in question if it can be of any help:

Start-Date: 2017-10-11 09:06:14
Commandline: apt upgrade
Requested-By: ghislain (1000)
Upgrade: poppler-utils:amd64 (0.57.0-2ubuntu2, 0.57.0-2ubuntu4), libseccomp2:amd64 (2.3.1-2.1ubuntu2, 2.3.1-2.1ubuntu3), update-manager-core:amd64 (1:17.10.10, 1:17.10.11), gnome-session-common:amd64 (3.26.1-0ubuntu1, 3.26.1-0ubuntu2), gir1.2-mutter-1:amd64 (3.26.1-1, 3.26.1-2), update-manager:amd64 (1:17.10.10, 1:17.10.11), libmutter-1-0:amd64 (3.26.1-1, 3.26.1-2), ubuntu-session:amd64 (3.26.1-0ubuntu1, 3.26.1-0ubuntu2), mutter-common:amd64 (3.26.1-1, 3.26.1-2), ubuntu-docs:amd64 (17.10.6, 17.10.7), python3-distupgrade:amd64 (1:17.10.6, 1:17.10.7), python3-update-manager:amd64 (1:17.10.10, 1:17.10.11), ubuntu-release-upgrader-core:amd64 (1:17.10.6, 1:17.10.7), gnome-session-bin:amd64 (3.26.1-0ubuntu1, 3.26.1-0ubuntu2), libjpeg-turbo8:amd64 (1.5.2-0ubuntu3, 1.5.2-0ubuntu4), ubuntu-release-upgrader-gtk:amd64 (1:17.10.6, 1:17.10.7), unattended-upgrades:amd64 (0.97ubuntu2, 0.98ubuntu1), libpoppler-glib8:amd64 (0.57.0-2ubuntu2, 0.57.0-2ubuntu4), libpoppler68:amd64 (0.57.0-2ubuntu2, 0.57.0-2ubuntu4), mutter:amd64 (3.26.1-1, 3.26.1-2), libclutter-gtk-1.0-0:amd64 (1.8.4-1, 1.8.4-2)
End-Date: 2017-10-11 09:06:23

Since these updates, I can no longer use two-finger scrolling but still can enable edge-scrolling as a substitute.