For one thing, image based distros are very convenient. If you tell someone "Just install Bazzite", they will probably have a nice gaming experience without any tinkering, because everything is already set up for you ootb.
You have to understand the concept first. Fedora Atomic/ image based distros are built from top to bottom, not on the same level. If something changes from "above", your install will change too, to an 1:1 copy basically.
Problem is, if stock Fedora isn't allowed to ship/ doesn't have some things pre-installed, it's harder to iron out on the user level, e.g. by negatively affecting update times.
uBlue is basically a "build script", that takes the upstream image, modifies it, and redistributes that with the changes included.
In that way, the image from other users is the same as yours, with the same bugs.
This makes it more efficient and user friendly.
It also allows devs to make their "own" distro with only their changes included, while offering a very solid base they don't have to maintain themselves.
So what I understand uBlue is not to Fedora Atomic as Nobara is to Fedora?
Like, I can install Silverblue and get anything with rpm-ostree, but that is an overlay on the tree (like a git patch) instead of simple changing the files like on regular distro. Because of that swapping base of the tree to new or different version take computing time, so people are free to build custom base to their needs for convenience. And uBlue is a system to build those images easly. Do it get it right? 😅
The more packages you install rpm-ostree, the likelier your system will break. You effectively turn back to a traditional distro that relies on a package manager, so all the things that can go wrong with a package manager are bound to go wrong. The whole point of fedora atomic is to offload the OS composition (so all the complicated packages stuff) higher up the chain. So that not everyone mixes up their own combination of packages installed, but instead you get a (semi-) fixed combination of packages that has been tested to work already before it lands on your computer.
The uBlue images are just different package combinations - but still you're not the only one rocking the packages combination of bazzite for example, so it is rather unlikely you'll run into a problem that only you and nobody else has.
This to me is also what sets fedora atomic apart from Suse MicroOS for example. With MicroOS you still have a package manager messing about with the system, and once it makes a mistake that gets buried in your system forever, except if you notice, roll back and fix it. As where with fedora atomic the mechanism how your system layout comes to your computer is similar to how git works (ostree) or images (like docker, which is what ublue ships). So if there's a mistake in how your system is layed out, the next time you rebase/update you are guaranteed to end up with a the intended system layout.
Yes, basically. uBlue doesn't maintain distros, really, it just repackages Fedora Atomic with some minor changes (including non-free drivers, for instance). That way if you need the software they repackaged into the image (like Nvidia drivers), you don't have to use overlays, and instead can use uBlue images. In fact, you can actually rebase Fedora Atomic to uBlue and vice versa with a single command. All it does is change where the base images are fetched from, and it's a potentially easy way to switch between images without having to perform a reinstall (do note that different packages in the base may modify config files that will persist between rebases, though). I haven't personally tried it, so I don't know if there's a likelihood to run into issues, but it's an interesting option nonetheless.