There was this FPS demo recently https://playcanv.as/p/qxGSuzYq/

People have also converted some small sections of Unreal 5 demos into splats https://superspl.at/scene/692c4f91

Or perhaps use a real world scan - it was suggested this one would make an ideal setting for zombies https://superspl.at/scene/6359774f

Can someone explain the unreal demo linked here - is the reflection in the street also using splatting, or is it something else?

Yes splats do reflections