The recommended way of installing applications in postmarketOS is through the official package repositories from Alpine and pmOS. Advanced users may consider installing Flatpak to install additional applications from Flathub (or other Flatpak repositories).
$ sudo apk add flatpak
Why there is no postmarketOS-specific Flatpak repository
Flatpak has good sandboxing features. However, the packaging format is entirely different to APKBUILD, in syntax and in its philosophy. If we created our own Flatpak repository, we would have much more maintenance effort . Instead, the plan is to bring the sandboxing features to the existing packages with AppArmor.
- postmarketos#18 Evaluating privilege separation for postmarketOS and Alpine apps