I'm generally a Windows user, but on the verge of doing a trial run of Fedora Silverblue (just need to find the time). It sounds like a great solution to my.. complicated... history with Linux.

I've installed Linux dozens of times going back to the 90s (LinuxPPC anyone? Yellow Dog?), and I keep going back to Windows because I tweak everything until it breaks. Then I have no idea how I got to that point, but no time to troubleshoot. Easily being able to get back to a stable system that isn't a fresh install sounds great.

An immutable distro, to my understanding, locks core components of Linux (mainly /sys afaik) from interaction from not only bad actors but also the user so that you can't fuck up you're system in a way like Linus from LTT (removing X11 by forcefully ignoring all warnings). Applications can be installed as Flatpak, AppImage, Snap or through OverlayFS from regular repositories.

Advantages to (non- tech savvy) users are an additional layer against their own mistakes and easier support since the important stuff is identical on every install of the given distro.

It's not just about malware, but more about system stability and avoiding breaking your system by bad updates. Updates are atomic (all or nothing) Ideally if something goes wrong, the update isn't applied at all. If you manage to boot to a bad config, you can fix it by rebooting in to the previous known good config.

This is immensely valuable for appliance-type devices that aren't meant to be "administered" by end users, like the Steam-deck, set top boxes, even Android phones. For laptops / desktops I'm sure it has some value for people who want a stable base, with newer flatpak/AppImages for day to day use.

As for how updates and system packages are installed, I can't answer the specific technologies used, but I believe the principle is that an entirely new/complete filesystem "image" is created / layered on top. Then you reboot to the new image.