Adobe’s DNG converter is presented as " …The Adobe DNG Converter, a free utility that converts files from more than 350 cameras to DNG, enables you to easily convert camera-specific raw files to a more universal DNG raw file."
Imo, the issue is that DxO accepts Adobe’s files, but rejects those DNDs originating from unsupported cameras. That self-inflicted limitation keeps PhotoLab from being usable for everyone. I appreciate DxO’s ambitions for perfection, but implemented as it is now, this ambition turns into a weakness.