Preparei nesta dica uma lista de repositórios que contém pacotes que não estão inclusos nos repositórios oficias do Ubuntu 20.10. Para habilitá-los use o terminal, cole os comandos em negrito (sem "$") e digite sua senha, após o adicionar o repositório desejado digite o comando "sudo apt update" para que os pacotes fiquem disponíveis para instalação.

1. Navegador Google Chrome - https://www.google.com/intl/pt-BR/chrome/

wget -q -O - https://dl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
sudo sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" > /etc/apt/sources.list.d/google-chrome.list'

2. Navegador Opera - https://www.opera.com/pt-br

sudo add-apt-repository 'deb https://deb.opera.com/opera-stable/ stable non-free' -y
wget -qO - https://deb.opera.com/archive.key | sudo apt-key add -

3. Navegador Vivaldi - https://vivaldi.com/pt-br/

wget -qO- https://repo.vivaldi.com/archive/linux_signing_key.pub | sudo apt-key add -
sudo add-apt-repository 'deb https://repo.vivaldi.com/archive/deb/ stable main' -y

4. Navegador Brave - https://brave.com/

wget -qO - https://brave-browser-apt-release.s3.brave.com/brave-core.asc | sudo apt-key --keyring /etc/apt/trusted.gpg.d/brave-browser-release.gpg add -
echo "deb [arch=amd64] https://brave-browser-apt-release.s3.brave.com/ stable main" | sudo tee /etc/apt/sources.list.d/brave-browser-release.list

5. Navegador Firefox (PPA oficial, mantém atualizado sempre que uma nova versão é lançada)

sudo add-apt-repository ppa:ubuntu-mozilla-security/ppa -y

6. Lutris - https://lutris.net/

sudo add-apt-repository ppa:lutris-team/lutris -y

7. Spotify - https://www.spotify.com/br/

echo "deb http://repository.spotify.com stable non-free" | sudo tee /etc/apt/sources.list.d/spotify.list
wget -qO - https://download.spotify.com/debian/pubkey.gpg | sudo apt-key add -

8. Google Earth - https://www.google.com.br/earth/

wget -qO - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
sudo sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/earth/deb/ stable main" > /etc/apt/sources.list.d/google-earth-pro.list'

9. VirtualBox - https://www.virtualbox.org/

wget -q http://download.virtualbox.org/virtualbox/debian/oracle_vbox_2016.asc -O- | sudo apt-key add -
echo "deb [arch=amd64] http://download.virtualbox.org/virtualbox/debian focal contrib non-free" | sudo tee /etc/apt/sources.list.d/virtualbox.list

10. Java - https://launchpad.net/~linuxuprising/+archive/ubuntu/java

sudo add-apt-repository ppa:linuxuprising/java -y

11. MegaSync - https://mega.nz/sync

wget -qO - https://mega.nz/linux/MEGAsync/xUbuntu_20.04/Release.key | sudo apt-key add -
sudo sh -c 'echo "deb http://mega.nz/linux/MEGAsync/xUbuntu_20.10/ ./" > /etc/apt/sources.list.d/megasync.list'

12. Dropbox - https://www.dropbox.com/

wget -c http://biglinux.lua.im/mirror/biglinux/packages/focal/main/dropbox-repository_1.0.0-1big1_all.deb
sudo dpkg -i *dropbox*.deb; rm *dropbox*.deb

13. qBittorrent - https://www.qbittorrent.org/download.php

sudo add-apt-repository ppa:qbittorrent-team/qbittorrent-stable -y

14. Papirus icon theme - https://github.com/PapirusDevelopmentTeam/papirus-icon-theme

sudo add-apt-repository ppa:papirus/papirus -y

15. Enpass - https://www.enpass.io/

sudo sh -c 'echo "deb https://apt.enpass.io/ stable main" > /etc/apt/sources.list.d/enpass.list'
wget -O - https://apt.enpass.io/keys/enpass-linux.key | sudo apt-key add --

16. Kernel Xanmod - https://xanmod.org/

echo 'deb http://deb.xanmod.org releases main' | sudo tee /etc/apt/sources.list.d/xanmod-kernel.list
wget -qO - https://dl.xanmod.org/gpg.key | sudo apt-key add -

17. FreeOffice - https://www.freeoffice.com/pt/

wget -c http://biglinux.c3sl.ufpr.br/packages/focal/main/freeoffice-repository_1.0.0-1big1_all.deb
sudo dpkg -i *freeoffice*.deb; rm *freeoffice*.deb

18. Skype - https://www.skype.com/pt-br/

wget -q -O - https://repo.skype.com/data/SKYPE-GPG-KEY | sudo apt-key add --
echo "deb https://repo.skype.com/deb stable main" | sudo tee /etc/apt/sources.list.d/skype-stable.list

19. TeamView - https://www.teamviewer.com/pt-br/download/windows/

wget -O - https://download.teamviewer.com/download/linux/signature/TeamViewer2017.asc | sudo apt-key add -
sudo sh -c 'echo "deb http://linux.teamviewer.com/deb stable main" > /etc/apt/sources.list.d/teamviewer.list'

20. Microsoft Teams - https://www.microsoft.com/pt-br/microsoft-365/microsoft-teams/free

wget -q https://packages.microsoft.com/keys/microsoft.asc -O- | sudo apt-key add --
sudo sh -c 'echo "deb [arch=amd64] https://packages.microsoft.com/repos/ms-teams stable main" > /etc/apt/sources.list.d/teams.list'

SCREENSHOTS