Instalator sa, mimochodom, vola pitivi-setup.exe
toz asi mas nemocnej pocitac a/nebo nemocnej prohlizec :) v tebou citovanem textu je ten Installer tento link:
http://flatpak.pitivi.org/pitivi.installer.desktop
coz je normalni desktop file, tedy textovy soubor a provadi:
bash -c "cd `dirname %k`; echo 'Getting installation script from https://git.gnome.org/browse/pitivi/plain/build/flatpak/pitivi-flatpak'; wget https://git.gnome.org/browse/pitivi/plain/build/flatpak/pitivi-flatpak -P /tmp/ -O pitivi-flatpak > /dev/null 2>&1; chmod +x pitivi-flatpak; ./pitivi-flatpak --installer"