Just came across KB83346 that references a problem with mouse/keyboard not working on a certain Dell laptop. It seems to mention an issue with USB 3.0 and that you need to install a hotfix and also enable the option called "Always enable pre-boot USB support".
In my McAfee DE training material it states "It is better not to enable this option because Drive encryption dynamically enables USB on demand". Does anyone have this option enabled and would it cause any issues enabling it on already encrypted systems? I question why the KB states that it must be enabled when my training material states don't enable. Want to avoid any issues if I enable it per that KB article.
You should only use this option on machines which have USB bugs - for most machines it's not needed (as the training material says). It's designed for machines with buggy BIOS code.
I don't believe the "always enable USB" option is generally tested against all hardware - it's only tested in the case where the automatic enabling does not work.
And since most modern machines are now UEFI, it's becoming less relevant anyway. (UEFI machines have their own built-in USB support).