Follow these simple steps to start using Flatpak
elementary OS 5.1 and newer comes with Flatpak support out of the box. For non-curated apps, head to Flathub to install any app using the big "Install" button, and open the downloaded `.flatpakref` file with Sideload.
Note: After installing one app from a remote like Flathub, all other apps from that remote will also automatically show up in AppCenter.