Thanks very much Buddy and J¨¹rgen. There wasn't much of note in the launcher log. But disabling Wayland did the trick
Here are the steps to disable replace Wayland with Xorg for Debian 10 (Buster):
$?sudo vi /etc/gdm3/daemon.conf
Uncomment the line that disables Wayland, eg
[daemon]
# Uncomment the line below to force the login screen to use Xorg
WaylandEnable=false