Hidden away in the middle of the article from The Guardian:
A government spokesperson declined to comment on the paper on the grounds that it had not been published, and stipulated that as the document derived from the Northern Ireland executive it was “not a UK government policy document”.

She said: “Our policy is clear – we are committed to ensuring there is no hard border between Northern Ireland and Ireland and to ensuring the same unfettered access for Northern Ireland’s businesses to the whole of the UK’s internal market. We have set out our preferred customs models to enable trade to remain as frictionless as possible.”