I am asking the question in respect to current time.
Do scriptures provide any living people who can be treated as authentic (for decisions) in Hinduism without any doubt?
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Yes, the Dharma Shastras indicate who is an authority on Sanatana Dharma.
Learn that Dharma, which has been ever followed by, and sanctioned by the heart of, the learned and the good, who are free from love and hate.—(2.1)
'Learned' means those persons who have learned the Vedas through Adhyayanam, have learned the Vedangas, such as logic, Mimamsa (hermeneutics), and Sanskrit grammar.
'Good' means those persons strictly adhere to Dharma to the best of their ability, have kept their vow of celibacy during Brahmacharya (rare today), are not hypocrites, and teach whatever they follow.
'Free from love and hate' means these people care about the truth, are objective, and do not follow beliefs merely because they like them or dislike them, like many people in modern times do.
Here are the sources of Dharma:
The entire Veda is the root-source of Dharma; also the Conscientious Recollection of righteous persons versed in the Veda, the Practice of Good (and learned) Men, and their self-satisfaction.—(2.6)
'Conscientious Recollection of righteous persons versed in the Veda' refers to Smritis, such as the Dharma Shastras, Puranas, and Itihasas.
'the Practice of Good (and learned) Men' refers to living authorities who have learned the Vedas, have done Adhyayanam, follow the scriptures, etc.
And an important point to note is that the authority of the four things mentioned above is listed from most authoritative to least authoritative, such that if a qualified Guru says something against the Smriti or Veda, then that statement is not authoritative.
If the question should arise—“How should it be in regard to those points upon which the laws have not been declared?”—[the answer is]—what the cultured Brāhmaṇas declare, that shall be the undoubted law.—(12.108)
Those Brāhmaṇas, by whom the Veda, along with its supplements, has been learnt in the right manner, and who are guided directly by the revealed texts,—shall be regarded as ‘cultured.’—(12.109)
And it specifies who is not qualified to be an authority:
That which even a single Brāhmaṇa learned in the Veda decides to be the law, shall be understood to be the highest law,—and not what is asserted by ten thousand ignoramuses.—(12.113)