Gfilui

I'm running Ubuntu MATE 16.04 LTS.

I have added Flatpak PPA and installed it to my system:

sudo add-apt-repository ppa:alexlarsson/flatpak
sudo apt update
sudo apt install flatpak

And then I want to install some application as Flatpak, so I need to run some commands in the terminal (KDE as example):

1. 
   

   to add repository:

   
   
   

   flatpak remote-add --if-not-exists flathub 
   https://flathub.org/repo/flathub.flatpakrepo
   flatpak remote-add --if-not-exists kdeapps --from 
   https://distribute.kde.org/kdeapps.flatpakrepo
   

   
   


2. 
   

   to install needed flatpak (KDiff3 as example):

   
   
   

   flatpak install kdeapps org.kde.kdiff3
   

   
   

I have read about gnome-software-plugin-flatpak and plasma-discover-flatpak-backend, but there are no such packages for Ubuntu Xenial.

But I can't find solutions for Ubuntu 16.04 LTS.

Update 1: tried to build source package of plasma-discover from 18.04 LTS on 16.04 LTS but got many errors about Qt5 declarations such as

discover/libdiscover/resources/ResourcesModel.cpp:336:42: error: ‘qAsConst’ was not declared in this scope

for(auto backend: qAsConst(m_backends))

^

libdiscover/CMakeFiles/DiscoverCommon.dir/build.make:374: recipe for target 'libdiscover/CMakeFiles/DiscoverCommon.dir/resources/ResourcesModel.cpp.o' failed

so this is not a solution.

Update 2: installing GNOME Software from Snappy with snap install --edge gnome-software --classic allows to use Snap GUI, but not FlatPak.