I'm using a dual display configuration (Windows 10 2004). When using the Grid mode on the main display, the Home/Ctrl+Home and End/Ctrl+End key have the expected effect (going to the first or last image in the Grid).
When using the Grid mode on the secondary display, these keys have no effect. I didn't notice this before version 9.3 but I'm not sure.
Updates to the Adobe Photography Products were released yesterday and include a fix for this issue. Please install the December update, restart your system and verify you are no longer experiencing the issue. Thank you for your assistance in reporting, providing additional information and, most of all, for your patience.