Hi JanetBiggar
Thanks for the suggestion. I have not tried plugging in external devices, but it's certainly worth a shot. I overwrote Lite with MX Linux so it may take a while to get around to giving Lite another go. The problem is particular to this notebook and Lite because Lite installed OK on a desktop and there have been no similar problems recorded in the Forum. So it's an isolated instance.
Before installing MX I tried Lite 3.8 thinking it might be an issue with 4.0, but the same thing happened - unresponsive trackpad and keyboard at the login screen. Also worth noting is that the log in screen is at a low resolution indicating that the Nouveau driver did not load.
UPDATE: The problem is solved. The EFI partition had a few leftovers from previous installs of other distros. One or more of these must have been interfering with the boot.
Not sure how to mark this topic as solved