Have you ever seen Linux Journey? It’s a very informative set of tutorials on how Linux fundamentally works under the hood; all the separate systems that together create an operating system. The concepts you learn there will apply to almost any distro in some way, even if some distros (like Atomic ones) don’t let you mess with all of it.

For more top-level transition concerns, given that you’re coming from stock Debian running KDE… Bazzite can also run KDE, so provided you select KDE when you download it, your GUI experience should be pretty much identical. Some minor but important differences would include themes, but there are guides for that, too.

When it comes to package management, the intent on Atomic systems is you basically don’t install traditional packages (Flatpaks are the preferred option), but Bazzite has frameworks in place such that you can install pretty much any package from any distro, as laid out in their documentation I linked in my previous post and just now. Work is also ongoing to make traditional package-based software installations more seamless with an incoming switch from rpm-ostree to bootc, but that’s getting into the weeds. If you have a deb file for a GUI program that’s not available as a Flatpak, you’ll be using a Distrobox to install it.

If you have any specific concerns about the differences, let me know and I can hopefully give you more details.