If your Ubuntu installation locks up as the graphical boot screen attempts to initialize, and you can't get access to your system after starting it up, booting into a previous version can be a help.
This can happen after updating to the the latest update to Linux 4.4.0-108 kernel, which included a fix for the Meltdown vulnerability.
The default PDF-reader in Ubuntu 16.04 is very plain and non-configurable, but it is easy to replace it with a better alternative, such as qpdfview, which is much more configurable.
I always add these GNOME extensions to fix a few annoying quirks in Ubuntu Gnome (20.04), they should be included by default in Ubuntu, in my opinion. Arc Menu requires gnome-tweaks:
Since you can't change mp3 "Open with" "Default application" from Audacious to fx VLC under Properties in Ubuntu 16.04, and it is annoying to get your playlist deleted every time you open a single mp3-file, here is a work-around.
Go to File > Settings > Playlist and uncheck "Clear the playlist when opening files".
When you reply to a message or create a new message in Thunderbird, the default format is "Paragraph".
To change it to "Body Text", deactivate the "Use Paragraph format..." option under Edit > Preferences > Composition > General, and the default paragraph format changes from "Paragraph" to "Body Text".
With Scrapy you can crawl web sites and get their content, mainly text and images. Since it isn't possible to install Scrapy with sudo apt-get install scrapy, the recommended way is to install it inside a virtual Python environment called Anaconda.
With these commands you can get Scrapy up and running on Ubuntu 16.04: