Ubuntu update disasters

Ubuntu has announced that its 18.04 edition will live ten years to corner the Internet of Things.  The disastrous update failures described below do not give confidence. Within half a year the first killed my laptop usage for two days, the second for a full month.

Update failure 1: login stuck in loop.   In January 2019 the Ubuntu software updater put me into a nasty endless login loop.  The recipe then is to hit CNTRL + ALT + F3 (or F1 or F2) to start a terminal-like login screen; this worked, be it haphazardly needing multiple reboots.  When that screen appeared it was better to install and switch to the lightdm display manager which opens this CNTRL + ALT + F3 screen reliably.  The standard recipes are then to check the ownership of .Xauthority, the permissions of /tmp, and to muck with the nvidia driver, but in my case the culprit was the workspace grid Gnome extension in ~/.local/share/gnome-shell/extensions.  Its removal made Ubuntu finally start up; renewal from the extension page revived my workspace layout.  This update failure cost me two days of frantic googling until I found the answer.

Update failure 2: CPU frequency lowered.   In April 2019 the Ubuntu software updater again acted disastrously: after the mandatory restart my Portégé X30 became terribly slow.  It took three weeks to find the cause and remedy given here while the culprit remains unidentified.  I had already tried a complete Ubuntu 18.04 re-install; repeating all its fine tuning took another week.  Thanks, Ubuntu!