Aha. Success!
Wolfmans suggestion alone didn’t cut it, but monsta’s advice seems to have cleared the path. I got an updated Mate which is what I wanted.
Now, the 4K resolution on a 13.3" screen suggests a microscope for reading the menus, and perhaps that’s what Dell wanted to spare me from. But that should be fixable. Thanks A LOT guys, you’ve made my day!