sudo apt install flatpak
flatpak --user remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

Add to bashrc:

export XDG_CONFIG_HOME=$HOME/.config
export XDG_CACHE_HOME=$HOME/.cache
export XDG_DATA_HOME=$HOME/.local/share

Do not forget to add –user to all flatpak commands:

flatpak --user install flathub org.zim_wiki.Zim

Now reboot!

Interesting Flatpaks:

com.spotify.Client
org.zim_wiki.Zim
org.gottcode.FocusWriter
com.slack.Slack

How to use Flatpak