Upon updating the factory baseline of PureOS distribution by means of triggering “Reboot & Install” process in GNOME Software application, 90 packages have been successfully installed or upgraded from the Purism repository as of
2017.10.02 that is Oct 2, 2017:
% tail /etc/apt/sources.list
deb http://repo.puri.sm/pureos/ green main
However, the upgraded GDM3 service fails to initialize a flickering display while the login prompt is only presented on the virtual terminals (in text mode). Is there some way to rollback the latest PureOS update, or perhaps the GDM service to its original behaviour?