If pureos is going to use flatpak please provide all packages in flatpak format. I mean the whole operating system.
Don’t mix package formats like flatpak with deb.It will be a headache for both new and experienced users.
Have you looked at other package formats.
1.orbital apps (https://www.orbital-apps.com/)
2.gnu guix (https://www.gnu.org/software/guix/)
3.appimage(http://appimage.org)
4.snap (http://snapcraft.io/)
Orbital apps are secure (https://www.orbital-apps.com/documentation/security)