Comment 83 for bug 1779827

I'm happy to report that I was able to boot normally with gdm now, and it didn't get stuck. Yesterday I removed and reinstalled gdm3 and ubuntu-desktop, as suggested here, rebooted, but it was still the same (i.e. stuck in reboot), so I switched back to lightdm. Today when I turned it on it started normally using gdm (although I don't remember switching it to gdm again!).

This is the dpkg log, in case it helps someone - the problem started after July 3rd, and was solved after July 10th:
2018-07-03 09:56:21 install linux-cloud-tools-4.15.0-24:amd64 <none> 4.15.0-24.26
2018-07-03 09:56:21 install linux-cloud-tools-4.15.0-24-generic:amd64 <none> 4.15.0-24.26
2018-07-03 09:56:21 install linux-modules-4.15.0-24-generic:amd64 <none> 4.15.0-24.26
2018-07-03 09:56:25 install linux-image-4.15.0-24-generic:amd64 <none> 4.15.0-24.26
2018-07-03 09:56:26 install linux-modules-extra-4.15.0-24-generic:amd64 <none> 4.15.0-24.26
2018-07-03 09:56:38 install linux-headers-4.15.0-24:all <none> 4.15.0-24.26
2018-07-03 09:57:03 install linux-headers-4.15.0-24-generic:amd64 <none> 4.15.0-24.26
2018-07-03 09:57:19 install linux-tools-4.15.0-24:amd64 <none> 4.15.0-24.26
2018-07-03 09:57:20 install linux-tools-4.15.0-24-generic:amd64 <none> 4.15.0-24.26
2018-07-04 11:58:33 install lightdm:amd64 1.26.0-0ubuntu1 1.26.0-0ubuntu1
2018-07-04 11:58:34 install libgeoclue0:amd64 <none> 0.12.99-4ubuntu2
2018-07-04 11:58:34 install libnm-util2:amd64 <none> 1.10.6-2ubuntu1
2018-07-04 11:58:35 install libnm-glib4:amd64 <none> 1.10.6-2ubuntu1
2018-07-04 11:58:35 install geoclue:amd64 <none> 0.12.99-4ubuntu2
2018-07-04 11:58:35 install geoclue-ubuntu-geoip:amd64 <none> 1.0.2+18.04.20180223-0ubuntu1
2018-07-04 11:58:35 install libpanel-applet3:amd64 <none> 1:3.26.0-1ubuntu5
2018-07-04 11:58:36 install indicator-applet:amd64 <none> 12.10.2+17.10.20170425-0ubuntu1
2018-07-04 11:58:36 install indicator-application:amd64 12.10.1+17.04.20161201-0ubuntu1 12.10.1+17.04.20161201-0ubuntu1
2018-07-04 11:58:36 install liburl-dispatcher1:amd64 <none> 0.1+17.04.20170328-0ubuntu4
2018-07-04 11:58:37 install indicator-datetime:amd64 15.10+17.10.20170829.2-0ubuntu4 15.10+17.10.20170829.2-0ubuntu4
2018-07-04 11:58:37 install liblightdm-gobject-1-0:amd64 <none> 1.26.0-0ubuntu1
2018-07-04 11:58:37 install indicator-keyboard:amd64 0.0.0+18.04.20180216-0ubuntu1 0.0.0+18.04.20180216-0ubuntu1
2018-07-04 11:58:37 install indicator-messages:amd64 13.10.1+17.04.20170120-0ubuntu2 13.10.1+17.04.20170120-0ubuntu2
2018-07-04 11:58:38 install indicator-power:amd64 12.10.6+17.10.20170829.1-0ubuntu4 12.10.6+17.10.20170829.1-0ubuntu4
2018-07-04 11:58:38 install indicator-session:amd64 17.3.20+17.10.20171006-0ubuntu1 17.3.20+17.10.20171006-0ubuntu1
2018-07-04 11:58:39 install ubuntu-touch-sounds:all <none> 15.08
2018-07-04 11:58:39 install unity-greeter:amd64 18.04.0+18.04.20180314.1-0ubuntu2 18.04.0+18.04.20180314.1-0ubuntu2
2018-07-04 11:58:40 install indicator-sound:amd64 12.10.2+18.04.20180420.3-0ubuntu1 12.10.2+18.04.20180420.3-0ubuntu1
2018-07-04 16:12:19 install libhavege1:amd64 <none> 1.9.1-6
2018-07-04 16:12:20 install haveged:amd64 <none> 1.9.1-6
2018-07-06 17:44:45 install linux-modules-4.15.0-26-generic:amd64 <none> 4.15.0-26.28
2018-07-06 17:44:49 install linux-image-4.15.0-26-generic:amd64 <none> 4.15.0-26.28
2018-07-06 17:44:49 install linux-modules-extra-4.15.0-26-generic:amd64 <none> 4.15.0-26.28
2018-07-06 17:45:00 install linux-headers-4.15.0-26:all <none> 4.15.0-26.28
2018-07-06 17:45:25 install linux-headers-4.15.0-26-generic:amd64 <none> 4.15.0-26.28
2018-07-09 22:27:46 install linux-cloud-tools-4.15.0-26:amd64 <none> 4.15.0-26.28
2018-07-09 22:27:46 install linux-cloud-tools-4.15.0-26-generic:amd64 <none> 4.15.0-26.28
2018-07-09 22:27:49 install linux-tools-4.15.0-26:amd64 <none> 4.15.0-26.28
2018-07-09 22:27:50 install linux-tools-4.15.0-26-generic:amd64 <none> 4.15.0-26.28
2018-07-10 17:59:06 install gdm3:amd64 <none> 3.28.2-0ubuntu1.3
2018-07-10 17:59:07 install ubuntu-desktop:amd64 <none> 1.417