Nintendo DS support is already there and it works on my side with melonDS: select the melonDS executable, select the ROMs folder, choose Nintendo DS if auto-detect does not pick the platform type (works on my side), then scan.
Can you tell me exactly what you selected in each field?
Emulator app:
ROMs / games folder:
Platform selected:
melonDS install type: native package, AppImage, Flatpak, Snap, or something else?
The launcher currently scans `.nds` and `.dsi` for Nintendo DS.
Also, please share the screenshots
