You have no idea what a corrupt transmission is and you ignored the multiple translations which teach the same thing using the phrases all flesh and all peopleUsing corrupt translations serves to continue to deceive you. Israel is God's Bride. Let's ask her what her Bible says. The best English translation is still the Authorized Version. Why don't you quote from that? Why do you want to confuse the issue by bringing corrupt translations into the conversation? Let's use the Masoretic texts. They are as close to the originals you can get.
Joel 2:28 (NASB95) — 28 “It will come about after this That I will pour out My Spirit on all mankind; And your sons and daughters will prophesy, Your old men will dream dreams, Your young men will see visions.
Joel 2:28 (LEB) — 28 And it will happen afterward thus: I will pour out my Spirit on all flesh, and your sons and your daughters will prophesy, and your elders will dream dreams; your young men shall see visions.
Joel 2:28 (KJV 1900) — 28 And it shall come to pass afterward, That I will pour out my spirit upon all flesh; And your sons and your daughters shall prophesy, Your old men shall dream dreams, Your young men shall see visions:
Joel 2:28 (UASV) — 28 “And it will happen afterward, that I will pour out my Spirit on all flesh; your sons and your daughters will prophesy, your old men will dream dreams, and your young men will see visions.
Joel 2:28 (NIV) — 28 “And afterward, I will pour out my Spirit on all people. Your sons and daughters will prophesy, your old men will dream dreams, your young men will see visions.
all people, all flesh mankind
That is not Hebrews only
See further below for a discussion on your faulty use of the negative inference fallacy
The Spirit is to be poured out on all
And all nations are to see salvation
Isa 49:6He says, “It is too small a thing that You should be My Servant To raise up the tribes of Jacob and to restore the preserved ones of Israel; I will also make You a light of the nations So that My salvation may reach to the end of the earth.”
that is a promise of salvation to nations unto the end of the earth.
Ps 67:2That Your way may be known on the earth, Your salvation among all nations.
A PROMISE OF SALVATION TO ALL NATIONS
And all nations are to be blessed
Genesis 18:18 (NASB 95) — 18 since Abraham will surely become a great and mighty nation, and in him all the nations of the earth will be blessed?
A promise of blessings for all nations.
Gen 22:18 In your seed all the nations of the earth shall be blessed, because you have obeyed My voice
As Abram is the father of all nations
”Gen 17:5“ No longer shall your name be called Abram, But your name shall be Abraham; For I will make you the father of a multitude of nations.
You quite commonly employ the negative inference fallacy. You read what is in one verse and assume it limits an action or inclusion when it does not say so, and then you ignore the additional verses that show the extension of the act or inclusion.
For a General Example of the negative inference fallacy
Paul stating Christ died for him
Galatians 2:20 (NASB 95) — 20 I have been crucified with Christ; and it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself up for me.
Reading the verse, you cannot assume Christ died for Paul alone.
However in your case, you assume a covenant entrance of only Hebrews, ignoring many texts that bring the Gentiles into the covenant.