What is the authenticity of the hadith narrated from the Prophet, may Allah’s prayers and peace be upon him, concerning the one who drinks alcohol on the Day of Resurrection, which describes his state in the Hereafter and mentions that he will be treated like an idol worshiper?

This Hadith is not authentic. It has been narrated from Abdullah ibn Umar, may Allah be pleased with them both, through five chains of transmission, all of which are weak or fabricated.

Similarly, a similar narration has been reported from Amr ibn al-Aas or from Ubaydullah ibn Abdullah ibn Amr ibn al-Aas, as his own statement, and it is also weak.

As for greeting an alcoholic and visiting him when sick, a weak narration has been reported concerning it from Abdullah ibn Amr ibn al-Aas.

It is permissible to boycott an alcoholic for the sake of Allah if there is a شرعية (legitimate, Shar’i) benefit in doing so, especially for someone who openly commits the sin.

As for the phrase, "If he dies, then he is with Allah, the Almighty, like an idol worshipper," it has been reported through several chains of transmission. Although most of these chains are not free from defects and weakness, Sheikh Al-Albani considers the Hadith, due to the sum of its chains, to be حسن (good) or صحيح (authentic).