Follow these simple steps to start using Flatpak
To install Flatpak, set NixOS option
by putting the following into your
services.flatpak.enable = true;
Then, rebuild and switch to the new configuration with:
$ sudo nixos-rebuild switch
For more details see the NixOS documentation.
Flathub is the best place to get Flatpak apps. To enable it, run:
$ flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
Now all you have to do is install some apps!