The D415's focal length is 1.88 mm. On the D435 model it is 1.93 mm.
You can find detailed information on the 400 Series cameras' hardware settings and structure in their data sheet documents.
This one covers the whole 400 Series, including module circuit boards.
Whilst this older one covers the D415 and D435 only.
Edit: I recalled that the Logitech Brio was a 4K camera that was well received at its time of release. It has a default FOV of 90 degrees but can be set to 78 degrees with an optional software download, according to its spec sheet.