Firefox on Debian stable is so old that websites yell at you to upgrade to a newer browser. And last time I tried installing Debian testing (or was it debian unstable?), the installer shat itself trying to make the bootloader. After I got it to boot, apt refused to work because of a missing symlink to busybox. Why on earth do they even need busybox if the base install already comes with full gnu coreutils? I remember Debian as the distro that Just Wroks™, when did it all go so wrong? Is anyone else here having similar issues, or am I doing something wrong?
Debian is working as intended. You are wanting to use Ubuntu or Mint if you want more up to date packages.
They can just use Flatpak as it will be the newest outside of Arch. Alternatively they could run Distrobox with something like Fedora.
I stopped using flatpak when I found out both I had to update outside of the package manager. Also using flatpak gave me some issues with my sound card, so I just run the .deb. To each their own though, which is why I love Linux.
https://wiki.debian.org/DontBreakDebian
Installing outside packages is generally not a good idea. You can use Distrobox with a upstream distro like Fedora or you can use Debian Back ports.