DLC for Dragon Quest Builders is not functional without a ticket. In the NSP ecosystem, the DLC file contains the assets (models, textures), but the game looks for a digital "ticket" to prove you own it.
When searching for "Dragon Quest Builders SWITCH NSP -DLC-" , you want a release where the DLC is pre-packaged as [DLC].nsp and flagged as [Unlocked] to avoid requiring a linked Nintendo account. Dragon Quest Builders SWITCH NSP -DLC-
This package includes the full suite of DLC, expanding the "Terra Incognita" free-build mode with massive new features: DLC for Dragon Quest Builders is not functional
If you have obtained legal backups of your own game + DLC: When searching for "Dragon Quest Builders SWITCH NSP
Critical: The base game, update, and DLC must share the same Title ID (e.g., 0100BCC0061A8000). Mismatched regions (USA vs EUR) will fail.