In April 2021, programmer Matt Phillips revealed on Twitter that he included a complete native 4K port of TimeSplitters 2 in Homefront: The Revolution as an unlockable Easter egg in the same arcade machine used to access the first two levels which were previously found in 2016. Despite Phillips stating he lost the code to unlock the full port, Microsoft employee Spencer Perreault replied to Phillips with the correct code a few days later, and with its recovery several other codes to access much of the game's modes and content were discovered by fans.

While it is currently unknown how to access TimeSplitters 2's co-op mode, Phillips suggested that if someone could hack two or more arcade machines into a co-op map in Homefront: The Revolution, the game should boot to TimeSplitters 2's multiplayer menu.

A complete guide on how to unlock the port and known codes (as of April 9, 2021) is included in the source link.
Contributed by MehDeletingLater
The first two levels of Timesplitters 2 (Siberia and Chicago) can be found within Homefront: The Revolution. They are accessible using an arcade cabinet in the game's Restricted Zone. Although there are no texture/model differences, some elements of the GUI, particle effects, lighting, and weapons sounds are new.
Contributed by retrolinkx