This article provides a list of many popular applications PPAs for Ubuntu 16.04 LTS Xenial Xerus. It provides PPA addresses for LibreOffice, GIMP, Inkscape, Scribus, SimpleScreenRecorder, OpenJDK, even GNU Ring, and some more applications (I listed only free software here, please tell me if I made any mistake).
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Important note: every PPA is Personal meaning it could be created by any person. You may trust or distrust any of them, use one or not to use one. Use these PPA repositories on your own risk.
LibreOffice
https://launchpad.net/~libreoffice/+archive/ubuntu/ppa
sudo add-apt-repository ppa:libreoffice/ppa sudo apt-get update
sudo apt-get install libreoffice
SimpleScreenRecorder
sudo add-apt-repository ppa:maarten-baert/simplescreenrecorder sudo apt-get update
sudo apt-get install simplescreenrecorder
HandBrake
sudo add-apt-repository ppa:ricotz/experimental sudo apt-get update
sudo apt-get install handbrake
GIMP
https://launchpad.net/~otto-kesselgulasch/+archive/ubuntu/gimp
sudo add-apt-repository ppa:otto-kesselgulasch/gimp sudo apt-get update
sudo apt-get install gimp
Inkscape
https://launchpad.net/~inkscape.dev/+archive/ubuntu/stablesudo add-apt-repository ppa:inkscape.dev/stable sudo apt-get update
sudo apt-get install inkscape
Blender
https://launchpad.net/~thomas-schiex/+archive/ubuntu/blender
sudo add-apt-repository ppa:thomas-schiex/blender sudo apt-get update
sudo apt-get install blender
GRUB Customizer
https://launchpad.net/~danielrichter2007/+archive/ubuntu/grub-customizer
sudo add-apt-repository ppa:danielrichter2007/grub-customizer sudo apt-get update
sudo apt-get install grub-customizer
Boot Repair
https://launchpad.net/~yannubuntu/+archive/ubuntu/boot-repair
sudo add-apt-repository ppa:yannubuntu/boot-repair sudo apt-get update
sudo apt-get install boot-repair
Tor Browser
sudo add-apt-repository ppa:webupd8team/tor-browser sudo apt-get update
sudo apt-get install tor-browser
VLC
sudo add-apt-repository ppa:videolan/stable-daily sudo apt-get update
sudo apt-get install vlc
Scribus
https://launchpad.net/~scribus/+archive/ubuntu/ppa
sudo add-apt-repository ppa:scribus/ppa sudo apt-get update
sudo apt-get install scribus
Unetbootin
sudo add-apt-repository ppa:gezakovacs/ppa sudo apt-get update
sudo apt-get install unetbootin
Terminix
https://launchpad.net/~webupd8team/+archive/ubuntu/terminix
sudo add-apt-repository ppa:webupd8team/terminix sudo apt-get update
sudo apt-get install terminix
Ubuntu SDK
https://launchpad.net/~ubuntu-sdk-team/+archive/ubuntu/ppa
sudo add-apt-repository ppa:ubuntu-sdk-team/ppa sudo apt-get update
sudo apt-get install ubuntu-sdk-ide
Unity Desktop Environment
https://launchpad.net/~ubuntu-desktop/+archive/ubuntu/ppa
sudo add-apt-repository ppa:ubuntu-desktop/ppa sudo apt-get update
sudo apt-get install unity
Atom
https://launchpad.net/~webupd8team/+archive/ubuntu/atom/+index
sudo add-apt-repository ppa:webupd8team/atom sudo apt-get update
sudo apt-get install atom
GNOME Shell Extensions
https://launchpad.net/~gnome-shell-extensions/+archive/ubuntu/ppasudo add-apt-repository ppa:gnome-shell-extensions/ppa sudo apt-get update
Eclipse
https://launchpad.net/~mmk2410/+archive/ubuntu/eclipse-ide-java
sudo add-apt-repository ppa:mmk2410/eclipse-ide-java sudo apt-get update
sudo apt-get install eclipse-ide-java
Android Studio
https://launchpad.net/~paolorotolo/+archive/ubuntu/android-studio
sudo add-apt-repository ppa:paolorotolo/android-studio sudo apt-get update
sudo apt-get install android-studio
Chromium
https://launchpad.net/~saiarcot895/+archive/ubuntu/chromium-dev
sudo add-apt-repository ppa:saiarcot895/chromium-dev sudo apt-get update
sudo apt-get install chromium-browser
FreeCAD
https://launchpad.net/~freecad-maintainers/+archive/ubuntu/freecad-daily
sudo add-apt-repository ppa:freecad-maintainers/freecad-daily sudo apt-get update
sudo apt-get install freecad-daily
Y PPA Manager
https://launchpad.net/~webupd8team/+archive/ubuntu/y-ppa-manager
sudo add-apt-repository ppa:webupd8team/y-ppa-manager sudo apt-get update
sudo apt-get install y-ppa-manager
Qt Creator
Note: this is Qt Creator binary packages created from Git source code. Thus its name is qtcreator-git. This PPA is maintained by Alexander Drozdov.
sudo add-apt-repository ppa:adrozdoff/qtcreator-git
sudo add-apt-repository ppa:beineri/opt-qt561-xenial
sudo add-apt-repository ppa:adrozdoff/llvm-xenial
sudo add-apt-repository ppa:adrozdoff/cmake
sudo apt-get update
sudo apt-get install qtcreator-git
LightTable
sudo add-apt-repository ppa:dr-akulavich/lighttable sudo apt-get update
sudo apt-get install lighttable-installer
OpenJDK 7
sudo add-apt-repository ppa:openjdk-r/ppa sudo apt-get update
sudo apt-get install openjdk-7
OpenJDK 8
sudo add-apt-repository ppa:openjdk-r/ppa sudo apt-get update
sudo apt-get install openjdk-8
KDE Connect
sudo add-apt-repository ppa:vikoadi/ppa sudo apt-get update
sudo apt-get install kdeconnect
GNU Ring
sudo sh -c "echo 'deb https://dl.ring.cx/ring-nightly/ubuntu_16.04/ ring main' > /etc/apt/sources.list.d/ring-nightly-man.list"
sudo apt-key adv --keyserver pgp.mit.edu --recv-keys A295D773307D25A33AE72F2F64CD5FA175348F84
sudo add-apt-repository universe
sudo apt-get update && sudo apt-get install ring
The latest PPA for 16.04 mentioned here is GNU Ring and added at 30 November 2016.