What is the ruling on establishing proof against peoples whom the message of Islam has not reached, and are there peoples to whom messengers have not been sent, and how will proof be established against them?

We have previously discussed the people of the Fatrah (interval), those to whom the message did not reach, and how they will be tested. Allah Almighty has clarified that there were nations to whom He did not send messengers, as He said: ﴿O People of the Scripture, there has come to you Our Messenger making clear [the religion] to you after a long interval [fatrah] from the messengers.﴾