Sandboxin a GUI program.
 

Hello,
I want to install an application on Debian 10.6 x86_64, but I don't like this application hurt my system or steal anything from my Debian box. I found a list of Sandboxing applications and I need opinions about them:

1. SELinux
2. Mbox
3. Firejail
4. Flatpak

I want to run a GUI application.

Thank you.

What application?

They all suck, your best option is to macro a terminal command you like

This makes no sense in the context of the question the OP asked.

If you don't trust an application, you should not install it as root.

You can create a user account for the purpose of installing the application in ~/.local and running it as that user. The application will likely need to be compiled to run from ~/.local.

Then, be aware that X11 offers no security between client applications.

If you really don't trust an application, a dedicated machine or VM may be the best solution.
Ed

SELinux and sandboxing are useless? Thus, Sandboxing apps are toys?

I am somewhat familiar with AppArmor. It provides fine-grained access controls to limit possible damage resulting from security vulnerabilities. The assumption is that the application is benign but may have security vulnerabilities.

Since you asked about installing an application, you should be aware that installing as root already means that you trust the application.

What application are you worried about?
Ed