Change the mode of your Yubikey so that you can use it for PGP/GPG as well.
Fix graphics appearing in the subject line in Thunderbird
See how you can use your Yubikey to SSH into remote servers using a pin code.
A cheatsheet for yubikey.
Install this excellent screen recording tool in Ubuntu.
Install the Arc theme on Ubuntu.
Install the Atom text editor in Debian
Disable the onboard speaker to prevent it buzzing whilst you're working.
Install a much later (faster) version of Firefox in Debian 9.
Configure Emerald to maximise a window when you double-click the title bar.
Instructions for getting Compiz and Emerald working in Debian 9 Mate.
My base script to run after installing Debian 9 Mate.