/usr/share/xsessions/lxgames.desktop is in lubuntu-extra-sessions 0.39.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | [Desktop Entry]
# The names/descriptions should really be better
Name=LX Games
Comment=LX Games - A collection of games, using LXDE desktop.
Exec=/usr/bin/lxsession -s LX-Games -e LXDE
# Icon=
Type=Application
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