Thanks Valtam. I had searched for SMART and should have looked for S.M.A.R.T.
The utility showed up in the Accessories menu as "Disks". It would seem more logical in System along with "Partition Drives" (gparted), but I realise it comes as it comes. I have used
sudo nano /usr/share/applications/gnome-disks.desktop
and replaced the Categories line with simply
Categories=System;
which I reckon puts it in the right menu. I then used Settings/Main Menu/ to move it up above Partition Drives.