When do critical security updates hit PureOS?

[pajuky]

@purirocks

Am I installing a Flatpak app when I install from the Software app?

You need to check on the top right in the app details screen to see what source is selected.

If I use apt am I installing non-Flatpak?

apt + dpkg are the Debian package manager. This is different from Flatpak so your assumption was correct