Windows and fedora have them separate, I don’t know if this would require only updating plasma, or would need support from installers such as calamares.
Its an installer thing. Neon - which I assume is the operating system you refer to, i.e. contrary to Fedora and Windows, though you didn’t specify - uses the Ubuntu installer, and until the new jammy based Neon comes out - this is the old Ubuntu 22.04 installer.
In Ubuntu (also the new one) the installer is expected to be run by the main user of the new system and therefor it is much easier to ask all the user details during installation, and when the installation is done - you have a system that is ready to go.
The way Fedora does the “setup user account after installation” is quite complicated and requires creating a pre-setup user account on the installed system, that auto logins to a specific configuration that runs a “first time run wizard” that then needs to create a new account and then deletes the pre-setup account while logging out from the same account. This is quite a feat.
You can do something similar with an Ubuntu installer by using the “oem mode” (search for docs on it, or just select it from the live image boot menu) which was originally used to allow a computer OEM to build a “pre-installed OS” disk image and then efficiently duplicate it to all PCs that they sell with “Ubuntu pre-installed”. I haven’t tried that with Neon, and I don’t think that KDE has a “OEM pre-setup” environment, but maybe it will work well.
I don’t think Neon devs should invest in this scenario, but maybe OEMs such as Tuxedo computers have a solution for that (I have never owned a Tuxedo computer, so I have no idea how they handle this use case).
I was curious since this usecase can come up (espescially in oem scenarios), and wondered wheter or not something is planned or supported, and yeah, since plasma is no distro this would be hard to coordinate with the various installers to have support for it. Thanks for the answer!
Actually, neon has used Calamares for some time now. Kubuntu 24.04 now uses it as well. it does have an OEM option in its grub menu.
neon, just like other Ubuntu-like distros, use a simpler install process that more or less copies the compressed OS image in the ISO (also used for the live session) to disk, and does some configuration via chroot. Or something along that line. There is very little that is physically “installed.” I don’t think that the install process here, or on any Ubuntu based system, is very amenable to being split up here, but the OEM option might be useful for the purpose.