Those solutions seem more aimed at keeping the system clean vs isolating what resources a program can access. Flatpak does indeed get me part of the way there

Those solutions seem more aimed at keeping the system clean vs isolating what resources a program can access. Flatpak does indeed get me part of the way there with better isolation, but available apps seem so scatter shot that I need a fallback mechanism for when there is not an official Flatpak artifact. Distrobox makes a point of indicating they are not a security boundary.