@elscallr I agree about the instance configuration, fixing that is the real solution
My question was not about running something as another user, but about hiding the superadmin privileges from a single command I’d execute without switching users. However it is clear that something like that doesn’t exist so I’ll do the right thing and set everything to work with a new user
If the child is really young, check out the sugar desktop environment. There is an official distro from sugarlabs and there is also a fedora spin (fedora soas)
If the computer should be a little more functional, the GNOME desktop or the Deepin desktop are good options imo