Ben Turpin of Rockstar Intel showed VR mode in updated GTA: San Andreas of GTA: The Trilogy – The Definitive Edition. It is accessed using the command GTA.VR.1 in a debug menu. It seems the developers are using the same builds for creating VR version of the game for Oculus Quest 2 that was officially announced back in October.
To access the first person camera you need to type command GTA.VR.1 in Unreal Engine debug console. The use of mods and a debug menu is needed to access the feature since it's hidden away in the code of the game. Needless to say VR mode is unfinished since there are no official details on GTA: San Andreas for Oculus Quest 2 and no release date.