This passage from the description of the Border Ethereal (DMG p. 48) says that anything made of magical force can affect ethereal creatures:
A traveler on the Ethereal Plane is invisible and utterly silent to someone on the overlapped plane, and solid objects on the overlapped plane don’t hamper the movement of a creature in the Border Ethereal. The exceptions are certain magical effects (including anything made of magical force) and living beings.
Per the description of the magic missile spell (PHB p. 257), it is made of magical force; therefore, it should be able to affect ethereal creatures:
You create three glowing darts of magical force.
But in the description of the etherealness spell (PHB p. 238), it says that only things with a special ability or magic can affect ethereal creatures:
While on the Ethereal Plane, you can only affect and be affected by other creatures on that plane. Creatures that aren’t on the Ethereal Plane can’t perceive you and can’t interact with you, unless a special ability or magic has given them the ability to do so.
Magic missile has no text allowing it to affect ethereal creatures, and instead relies on the general rule for affecting ethereal creatures.
Which is right? Is etherealness just restating the rule in the DMG, or is it an explicit exception to how ethereal travel normally works?
Moreover, even if magic missile can affect ethereal creatures, does that mean that other spells which deal force damage can also affect ethereal creatures? Magic missile is explicitly made of “magical force”, but eldritch blast, which also deals force damage, is described as “crackling energy”. Is it also made of “magical force”?