To install Flatpak on Gentoo, open the Terminal app and run:
emerge --ask --verbose sys-apps/flatpakFlathub is the best place to get Flatpak apps. To enable it, run:
flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepoTo complete setup, restart your system. Now all you have to do is install apps!
Note: graphical installation of Flatpak apps may not be possible with Gentoo.