Ubuntu – After updating the Ubuntu from 18.04 to 20.04 Gnome Terminal is showing Unicode Characters?How to fix that

I've uploaded a Unicode test file which you should download and then cat in your terminal.

E.g.: cat ~/Downloads/Unicode-sample.txt and then use Shift+PgUp and Shift+PgDn in the terminal to verify whether all characters display correctly.

If you get the same results in your terminal as opening the original source file in your browser, your font is fine; otherwise, it's a dodgy font: use a different one. (I use "Envy Code R")

And once the terminal is fine, all applications running in the terminal will be fine as well!

The single long command for GNOME Shell removal is below

sudo apt purge adwaita-icon-theme gedit-common gir1.2-gdm-1.0 \
gir1.2-gnomebluetooth-1.0 gir1.2-gnomedesktop-3.0 gir1.2-goa-1.0 \
gnome-accessibility-themes gnome-bluetooth gnome-calculator gnome-calendar \
gnome-characters gnome-control-center gnome-control-center-data \
gnome-control-center-faces gnome-desktop3-data \
gnome-font-viewer gnome-getting-started-docs gnome-getting-started-docs-ru \
gnome-initial-setup gnome-keyring gnome-keyring-pkcs11 gnome-logs \
gnome-mahjongg gnome-menus gnome-mines gnome-online-accounts \
gnome-power-manager gnome-screenshot gnome-session-bin gnome-session-canberra \
gnome-session-common gnome-settings-daemon gnome-settings-daemon-common \
gnome-shell gnome-shell-common gnome-shell-extension-appindicator \
gnome-shell-extension-desktop-icons gnome-shell-extension-ubuntu-dock \
gnome-startup-applications gnome-sudoku gnome-system-monitor gnome-terminal \
gnome-terminal-data gnome-themes-extra gnome-themes-extra-data gnome-todo \
gnome-todo-common gnome-user-docs gnome-user-docs-ru gnome-video-effects \
language-pack-gnome-en language-pack-gnome-en-base language-pack-gnome-ru \
language-pack-gnome-ru-base language-selector-gnome libgail18 libgail18 \
libgail-common libgail-common libgnome-autoar-0-0 libgnome-bluetooth13 \
libgnome-desktop-3-19 libgnome-games-support-1-3 libgnome-games-support-common \
libgnomekbd8 libgnomekbd-common libgnome-menu-3-0 libgnome-todo libgoa-1.0-0b \
libgoa-1.0-common libpam-gnome-keyring libsoup-gnome2.4-1 libsoup-gnome2.4-1 \
nautilus-extension-gnome-terminal pinentry-gnome3 yaru-theme-gnome-shell

sudo apt autopurge

Note: if one have previously installed Vanilla GNOME desktop manually by sudo apt install vanilla-gnome-desktop and/or Ubuntu GNOME desktop by sudo apt install ubuntu-gnome-desktop and/or GNOME FlashBack by sudo apt install gnome-flashback gnome-panel and/or full GNOME by sudo apt install gnome - one have to execute extra removal commands below:

sudo apt purge adwaita-icon-theme geogebra-gnome gir1.2-gtd-1.0 \
gnome-accessibility-profiles gnome-applets-data gnome-audio gnome-backgrounds \
gnome-cards-data gnome-common gnome-desktop-testing gnome-dvb-daemon \
gnome-exe-thumbnailer gnome-extra-icons gnome-flashback-common \
gnome-humility-icon-theme gnome-hwp-support gnome-icon-theme \
gnome-icon-theme-gartoon gnome-icon-theme-gartoon-redux \
gnome-icon-theme-gperfection2 gnome-icon-theme-nuovo gnome-icon-theme-suede \
gnome-icon-theme-yasis gnome-mime-data gnome-nds-thumbnailer \
gnome-packagekit-data gnome-panel-control gnome-panel-data \
gnome-pkg-tools gnome-recipes-data gnome-remote-desktop gnome-settings-daemon-dev \
gnome-shell-pomodoro-data gnome-software-common gnome-software-doc \
gnome-theme-gilouche gnome-video-effects-extra gnome-video-effects-frei0r \
guile-gnome2-dev guile-gnome2-glib libgnome-autoar-doc libgnomecanvas2-common \
libgnomecanvas2-doc libgnomecanvasmm-2.6-doc libgnome-panel-doc libgnome-todo-dev \
libopenrawgnome7:amd64 libopenrawgnome-dev libreoffice-gnome libxine2-gnome:amd64 \
nautilus-sendto pidgin-gnome-keyring plymouth-theme-ubuntu-gnome-logo \
plymouth-theme-ubuntu-gnome-text ubuntu-gnome-wallpapers \
ubuntu-gnome-wallpapers-trusty ubuntu-gnome-wallpapers-utopic \
ubuntu-gnome-wallpapers-xenial ubuntu-gnome-wallpapers-yakkety

sudo apt autopurge

Then one can install any desktop environment of interest with commands like:

• Cinnamon - sudo apt install cinnamon-desktop-environment
• KDE as in Kubuntu - sudo apt install kubuntu-desktop^
• MATE as in Ubuntu MATE - sudo apt install ubuntu-mate-desktop^
• Unity - sudo apt install ubuntu-unity-desktop
• Xfce as in Xubuntu - sudo apt install xubuntu-desktop^

then reboot, select newly installed desktop session and login to it.

Note: this method is applicable for Ubuntu 20.10 too.