If you're a Once Human fan hoping for an FPS mode, you probably shouldn't as developer Starry Studio has no plans for one.
Like any time a third-person shooter releases, Once Human has some fans that would like a first-person mode, kind of ignoring the fact that when a game is built a particular way, something like that can break it in unexpected ways. As spotted by PCGamesN, an update was shared by Starry Studio responding to some commonly brought up topics, which also included things like character, controls, and the camera. Speaking on the FPS point, Starry wrote, "Including a first-person perspective may result in conflicts with the current game design. In response to your requests, we will consider adding first-person elements into future scenarios and game modes. However, we have no plans to add a first-person perspective to the game at present."
Essentially, don't expect it for the main game, if at all, as again it is a third-person game after all. In more positive news, Starry did also confirm that the 0.3 second delay before your character starts to move is being removed, writing, "The movement windup animation consists of about 20 movements and is quite intricate, so refining some of the details will require some time." It also noted that Vaulting is being upgraded, with a plan to change things so that "the character only begins vaulting after reaching a certain height," as right now you vault and jump at the same time.