Patch dropped, 1.7.36, that adds the FOV slider in game. Official link: https://bethesda.net/en/game/starfield/article/5IleyfqI44NacBQGGC20Km/starfield-updates-1-7-36-october-09-2023#:~:text=A new update has been,other performance and stability improvements
To save others from hunting, the two sliders, one for first person and one for third, are under Accessibility in Settings. I went looking for it under Display, or Interface, but I guess what do I know?
Curiously it also adds better support for Intel Arc GPUs. I would not have thought that was much of a priority but there you go.
For some reasons, a lot of game Dev's like to put FOV under Accessibility instead of display and I have no idea why lol.
-ST