WetGeek Perhaps you could use your file manager to look at the executable of an app you installed from a flatpak, and see if there's some obvious indication of a sandbox.
Flatpaks are sandboxed, although not entirely isolated, depending on the permissions granted. A user can check what permissions are granted by using the terminal command flatpak info -M $APPID.
This, for example, is the result for Zoom on my computer:
tomscharbach@ts-plasma-portable ~ $ flatpak info -M us.zoom.Zoom
[Context]
shared=network;ipc;
sockets=x11;wayland;pulseaudio;
devices=all;
filesystems=~/Documents/Zoom:create;~/.zoom:create;
[Session Bus Policy]
org.kde.*=own
org.freedesktop.ScreenSaver=talk
[Environment]
QT_QPA_PLATFORM=
Flathub has a GUI permissions manager available, but I don't use it because have no need for it. I use two Flatpaks, Edge and Zoom. Edge and Zoom are what they are, use what they use, and I'm not going to dink around with either.
In a loose and inexact way, I think of Flapak permissions as something akin to VirtualBox Guest Additions, granting an isolated instance access to services. The difference is, I think, that Flatpak permissions must be individually granted, while Guest Additions are more general.
WetGeek My only concern with flatpaks would be for users with limited storage on their systems. If they installed lots of flatpaks, they could end up with lots of copies of a common library or other dependency.
The practical reality is that devices with 16GB or 32GB disks are going to struggle with any mainstream distro, Flatpaks or not. I've never looked at it, but I wonder how many Flatpaks a user would have to install to use up even 1-2 GB's because of duplicated common libraries or dependencies.
