Tomb Raider Underworld will not display the FPS counter in the corner.

[Dura_Ace]

Even when it is enabled. Any work arounds? Any suggestions?

[Ogami]

Thats because Tomb Raider Underworld does not support the Steam Overlay.
Without the overlay you cant get the FPS counter ingame.
Nothing you can do, a lot of old games have problems with the Steam Overlay and Underworld is already 16 years old.

Its also listed on the PC Gaming Wiki as a unresolved issue:

Game does not support Steam overlay and no fix is yet known.

[かぐや]

Alt+Tab ↹ seems to be working flawlessly as a cheap fix.

[blunus]

https://steamcommunity.com/sharedfiles/filedetails/?id=1328254132

All you need is PID and Windows Run. Steam guide creaters do what PCGW don't.