How to fix broken locales in Raspberry Pi OS?

If you have some issue with seeing expected language both in command line as well as in GUI, don’t attempt to fix it by calling:

sudo raspi-config

Instead in your terminal open:

sudo vim /etc/default/locale

and ensure you have this exact content:

#  File generated by update-locale
LANG=en_US.UTF-8
LC_ALL=en_US.UTF-8
LANGUAGE=en_US.UTF-8

Now, reboot your Raspberry with:

sudo shutdown -r now