Does Allah ﷻ Punish Humans After They Die if Islam Hasn't Reached Them?

(Al Quran 3:108)  Allah does not will injustice for His creatures

Allah ﷻ does not will to punish people, in fact it is their own actions that will result in their punishment. Allah ﷻ only punishes those who knowingly and willingly reject His Message, He will not punish those who either didn’t get to hear His message or did hear but were unable to comprehend due to whatever valid reasons that He is aware of, as He is Truly All Knower and All Seer of each individual's life, as implied in the following verse: (Al Quran 6:131–132) And so it is that Your Sustainer would never destroy a community for its wrongdoing so long as its people are still unaware [of the meaning of right and wrong]: for all shall be judged according to their [conscious] deeds - and Your Sustainer is not unaware of what they do.

A very important lesson can also be derived from one of the most recited Surah of the entire Quran, Al Fatiha (The Opening), the last verse of which some of greatest thinkers of Islam have interpreted as identifying such people who never got the message of Islam or after receiving were unable to comprehend due to valid reasons: (Al Quran 1:07) the way of those upon whom You have bestowed Your blessings, not of those who have been condemned [by You], nor of those who go astray! - In his Message of the Quran - Muhammad Asad shares the views of Imam Ghazali (r.a) (9th Century Islamic Thinker) who held that the people described as "those who have been condemned" - that is, having deprived themselves of God's grace - are those who have become fully cognizant of God's message and, having understood it, have rejected it; while "those who go astray" are meant people whom the truth has either not reached at all, or to whom it has come in so garbled and corrupted form as to make it difficult for them to recognize it as the truth.[1]
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The above explanation of this verse indicates that there are people that Quran mentions who are not aware of the truth and they are ignorant therefore they will be judged accordingly and Allah ﷻ  is not unaware of their conditions. It is this reason why He separated "those who go astray" in this verse from "those who have been condemned" which means all who do not follow Islam are not by default under condemned category which would result in punishment in hereafter.

References:

[1] Muhammad Asad, Message of the Quran, Surah Al Fatiha (Opening) Verse 7