I considered that. Unfortunately silverblue doesn’t do live systems and aurora therefore doesn’t either. So a VM is the only way of trying it out. OP stated that they have someone to help with the actual installation so I left the whole create install medium for bare metal install out intentionally since I assume this person will be capable of helping with that.
Also small Markdown help: If you use dashes lemmy will automatically format bulletpoints correctly. You can’t use •s for it. Doesn’t take anything away from your comment, etcher is still the best tool to create a bootable usb drive, but for the future consider using dashes.
I would probably go with bluefin. KDE is great, I myself use aurora on one of my devices, but it can also be kinda fiddley with all of it’s options.
The user has never even used a PC and therefore won’t profit from the familiarity that KDE’s default desktop layout provides. Gnome on the other hand offers a more simplified experience with few options and big icons. All of that might be an asset here. You can use menulibre to hide menu entries from the menu and use the official documentation to remove command line access: https://help.gnome.org/admin/system-admin-guide/stable/lockdown-single-app-mode.html.en
Plus it’s still atomic which I actually think is helpful here. For once all the important system stuff is read only. Secondly if one manages to scream something up you can just rebase.