Where are the coordinates of the player's initial position listed?

Where are the coordinates of the player’s initial position in the Lyra Starter Game listed in the program?

Get actor locatationor world location and run an print string out of it

What I want to know is where the coordinates of the initial position of the players are written in the source code.

Not every code is included in the Source folder. (What you’re looking for might be in there, or might not be. It depends on the project. If it’s not determined using C++, you won’t be able to adjust it properly by editing any text folders.) If you want to change their initial location, you can do that either by using blueprints or C++. However if you only want to know their initial location, you can just print out that information after the Event Begin Play node like the other fella suggested.

The code for selecting Lyra player starts resides on
LyraGameMode.h
LyraGameModecpp
LyraPlayerSpawningManagerComponent.h
protected:
// Utility
APlayerStart* GetFirstRandomUnoccupiedPlayerStart(AController* Controller, const TArray<ALyraPlayerStart*>& FoundStartPoints) const;

LyraPlayerSpawningManagerComponent.cpp