I tried both Fedora-MATE and Ubuntu-MATE on the new (still nameless) laptop and found Ubuntu has a lot more configuration options. I like that. So then I started looking up how to "really enable" the root account on Ubuntu (possible), and how to install it on an 'already UEFI' machine (lots of old information, but quite possible now - not sure if I have found the 'currently best' method yet so I'll need to do more reading... #tomorrow