I have a lot of software installed, from various sources, and I would like to start using Flatpaks instead of PPA's. But how do I remove my current software entirely, with the PPA's and such? This is the output from my sudo apt update (I am using elementary os based on ubuntu 16.04Hit:1 http://ppa.launchpad.net/alexlarsson/flatpak/ubuntu xenial InReleaseHit:2 http://archive.canonical.com/ubuntu xenial InRelease                                                                                               Hit:3 http://ppa.launchpad.net/atareao/atareao/ubuntu xenial InRelease                                                                                   Hit:4 http://de.archive.ubuntu.com/ubuntu xenial InRelease                                                                                               Ign:5 http://dl.google.com/linux/chrome/deb stable InRelease                                                                                             Hit:6 http://download.virtualbox.org/virtualbox/debian xenial InRelease                                                                                  Hit:7 http://ppa.launchpad.net/bablu-boy/nutty-daily/ubuntu xenial InRelease                                                                             Hit:8 http://de.archive.ubuntu.com/ubuntu xenial-updates InRelease                                                                                Hit:9 http://de.archive.ubuntu.com/ubuntu xenial-backports InRelease                                                                              Hit:10 http://ppa.launchpad.net/djcj/vapoursynth/ubuntu xenial InRelease                                             Hit:11 http://dl.google.com/linux/chrome/deb stable Release                                    Hit:12 http://ppa.launchpad.net/elementary-os/stable/ubuntu xenial InRelease                                       Hit:13 http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu xenial InRelease                                       Get:14 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]                                        Hit:15 http://ppa.launchpad.net/kubuntu-ppa/backports/ubuntu xenial InRelease                                                  Hit:16 http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease                                                             Hit:17 http://ppa.launchpad.net/elementary-os/os-patches/ubuntu xenial InRelease                                               Hit:18 http://ppa.launchpad.net/webupd8team/java/ubuntu xenial InRelease                                                       Hit:19 https://deb.nodesource.com/node_7.x xenial InRelease                                              Hit:21 http://download.mono-project.com/repo/debian wheezy InRelease                                                    Hit:22 https://packagecloud.io/slacktechnologies/slack/debian jessie InReleaseLet's say, I want to remove Blender, MonoDevelop and LibreOffice entirely, so I could install it via Flatpaks later. How do I remove it?
Remove software and PPA's entirely
ubuntu;apt;elementary os;ppa
sudo apt-get autoremove --purge packagenameThen go through the /etc/apt/sources.list.d directory and remove any file referencing that repo.Also go through /etc/apt/sources.list and sources.list~ with sudo vi or sudo nano and remove or comment out the repository.Finally remove the GPG key for that repositorysudo apt-key listsudo apt-key del #A#A#A