hiya, i downloaded the community built kde plasma release of fedora 40, i want to try gnome but i dont want to wipe my kde settings etc. how would i be able to try gnome, and easily be able to switch back (preferably on bare metal not a vm)
Not easily, they’re built on two different library’s (QT and GTK) and as a consequence of their role use some of the same/similar configuration files, especially the user’s. Perhaps another machine to try Gnome on if you don’t want to/can’t use a VM.
You could use the live media to try it out without installing gnome at all?
If you do want to use it for sometime after installing it, you’ll need to install the whole stack. This can be (theoretically) uninstalled by rolling back the dnf transaction (but if you have more dnf transactions after this one, it may not work cleanly in practice). Look for dnf history undo in man dnf.
Gnome and KDE do share some common settings, but a lot of their configs are completely different. So, you could keep an eye of what new config files Gnome creates (~/.config/gnome* for example) and then remove them afterwords. Different apps that come with Gnome will also create their own configs/data directories in ~/.config, ~/.local and possibly other locations in your home dir.
You could use a new user for the Gnome tests if you wish, and use another one for KDE, and that way your user configs for the two will be completely separate.
Using separate hardware would likely be the safest and easiest, but in lieu of that, you could clone your current rootfs to create an experimental “branch” that you could easily throw away later. With a little effort, you can switch back and forth between your normal KDE install and the GNOME one you want to tinker with.
P.S. If you go that route, you might want to add exclude=kernel* to /etc/dnf/dnf.conf in both branches so you don’t have to deal with changes to your ESP/boot partition(s). The ESP/boot partition(s) will be shared between the OS instances in this configuration, so you need to be careful to not end up in a situation where there are kernels on the ESP/boot partition(s) that won’t work with one or the other of the branches because they don’t have that kernel version installed. If you intend to keep both branches long-term, you’ll have to work out your own system to keep the installed kernel versions in-sync between the two installs. (But for a short-term experiment, just not updating the kernel should be sufficient to avoid problems.)