I upgraded from 10.13.3 to 10.13.4. The mouse works on the built-in screen but not on an external monitor. A PRAM reset as in this thread did nothing. Increasing the size of the cursor as in this bug report shows the mouse pointer but not the I-beam cursor (text cursor), then increasing the size even more shows both cursors. Confusingly, a Quicktime recording of these changes shows the cursor always present, and always the same size.
I am using Dell U2414H. Any fixes better than this work-around?