For example, is a Black Dragonborn able to use its Breath Weapon, in this case, of acid type, to corrode walls, doors, objects, etc?
I'm asking this because when it comes to spells, they don't affect the environment unless it is specifically said so.
The Dragonborn race feature breath weapon is specific in what things it damages (my emphasis):
When you use your breath weapon, each creature in the area of the exhalation
There is no language in this that suggests it would affect objects. You can compare this against spells like fireball which state:
It ignites flammable objects in the area that aren't being worn or carried.
Also note that the spell dragon's breath contains the same limitation as the breath weapon for the race with no allowance for object damage.
The problem with allowing it is you've now increased the ability of the feature, and possibly of the similar spell effect that emulates the racial ability. Is it always on like fireball? Do they get to choose? Allowing this as a creative use will be up to a DM to determine, but doing so may raise questions rather than solve problems.
The Dragonborn's Breath Weapon has similar verbiage:
When you use your breath weapon, each creature in the area of the exhalation must make a saving throw, the type of which is determined by your draconic ancestry. ...[snip]... A creature takes 2d6 damage on a failed save, and half as much damage on a successful one.
Per a strict reading of RAW, the Dragonborn's Breath Weapon does NOT deal damage to objects.
Rules as Fun/Common Sense, however differ, in this DM's humble opinion. If a Dragonborn in my game wants to use their 1/rest resource to target and damage an/some object, then so-be-it. I wouldn't allow it to be used to damage attended/worn objects and it wouldn't change how spells interact with objects.
As written, it wouldn't, because the ability specifically calls out creatures.
The dragonborn's Breath Weapon trait says (PHB, p. 34; emphasis mine):
When you use your breath weapon, each creature in the area of the exhalation must make a saving throw, the type of which is determined by your draconic ancestry. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. A creature takes 2d6 damage on a failed save, and half as much damage on a successful one. The damage increases to 3d6 at 6th level, 4d6 at 11th level, and 5d6 at 16th level. After you use your breath weapon, you can’t use it again until you complete a short or long rest.
As a GM myself, I believe that this goes against the feel of the game and I allow it to damage unattended objects in the area. I think the wording was not an intentional attempt to ensure that the spell couldn't damage objects, but more a result of common wording used for a large variety of similar effects.
As written, however, it would not damage objects, as intended I do not think they even considered the option, and I would fall back to the rule of cool, as well as what the GM decided on for there specific game. It is certainly fair to say there wasn't enough acid, or it only affects certain types of matter, or other similar reasons for it to only affect creatures. For me, I like my dragonborn fire breathers to be able to start campfires with their breath weapons.
