File userChrome.css not working for Thunderbird/Firefox

Newer versions of Thunderbird and Firefox (starting around 2019) disable by default the loading of the 'userChrome.css' file used to configure display preferences. To enable it, you must enable via the Config Editor the setting called toolkit.legacyUserProfileCustomizations.stylesheets.

Reference: https://www.userchrome.org/how-create-userchrome-css.html

Display unified CJK characters in macOS terminal as Japanese characters

Without some specific language information (such as the "lang" attribute in HTML), unified CJK Unicode characters are displayed by default in a generic manner. However, users of a certain language would prefer to see the particular character version for that language even in the terminal.

This is possible in macOS by adding that language as a preferred one. For example, in order to display unified CJK characters in a macOS terminal as Japanese characters, you have to:

• Go to System Preferences > Language & Region
• Add the Japanese language to the "Preferred languages" panel

Note that you will need to restart the Terminal app before changes take effect.

Disable password prompting for updates in Ubuntu

If you want to run the Synaptic packet manager in Ubuntu/Lubuntu without it requiring a password, you must add a PolicyKit local definition. For this purpose create a file, named for instance /etc/polkit-1/localauthority/50-local.d/allow-user-update-wo-password.pkla, and add the following content to it:
[Allow User Updates Without Password]
Identity=*
Action=com.ubuntu.pkexec.synaptic
ResultAny=no
ResultInactive=no
ResultActive=yes

Customize GRUB2 menu colors in Ubuntu

The procedure for customizing GRUB2 menu colors in Ubunt is as follows:
1) Edit (or create) the file "/lib/plymouth/themes/default.grub" to add the appropriate menu color information.
Example:
# Color of the highlighted menu entry and its background within the menu box
set menu_color_highlight=yellow/dark-gray
# Color of non-selected menu entries within the menu box
set menu_color_normal=black/light-gray
# Color of the text and background outside the menu box
set color_normal=light-gray/black
2) Regenerate the the grub configuration file by running 'sudo update-grub'.

Customize other OS menu entries in GRUB2

The procedure for customizing menu entries for other OSes in GRUB2 is as follows:
1) Copy the menu entry you wish to customize from "/boot/grub/grub.cfg"
to "/etc/grub.d/40_custom".
2) Change the name of the menu entry as you wish.
3) Disable the OS prober to prevent regenerating the old menu entry by using the option "GRUB_DISABLE_OS_PROBER=true" in "/etc/default/grub".
4) Regenerate the the grub configuration file by running 'sudo update-grub'.