The Kingdom of God will be on earth. Jesus will return to earth (e.g., Acts 1:11) and become King on David’s throne in Jerusalem (Luke 1:32-33). Jeremiah prophesied about Jesus as king (calling him a “righteous Branch”):
5 “Behold, the days are coming, declares the Lord, when I will raise up for David a righteous Branch, and he shall reign as king and deal wisely, and shall execute justice and righteousness in the land. 6 In his days Judah will be saved, and Israel will dwell securely. And this is the name by which he will be called: ‘The Lord is our righteousness.’ (Jeremiah 23:5-6)
Note that he shall be king “in the land” (not in heaven).
All the saints (i.e., believers) will be part of the kingdom on earth:
and you have made them a kingdom and priests to our God, and they shall reign on the earth.” (Revelation 5:10)
That is why Jesus taught us to pray “Your kingdom come” (Matt 6:10).
For further information, see The Kingdom of God on Earth.
(Hbr 11:10, 13-14, 16 KJV) – “(10) For he looked for a city which hath foundations, whose builder and maker [is] God. … (13) These all died in faith, not having received the promises, but having seen them afar off, and were persuaded of [them], and embraced [them], and confessed that they were strangers and pilgrims on the earth. (14) For they that say such things declare plainly that they seek a country. … (16) But now they desire a better [country], that is, an heavenly: wherefore God is not ashamed to be called their God: for he hath prepared for them a city.”
“they desire a better (country), that is, an HEAVENLY” This is either a contradiction and the writer of Hebrews didn’t know what he was talking about. But wait someone els once talked about this kind of “place”.
(Jhn 14:2-3 KJV) – “(2) In my Father’s house are many mansions: if [it were] not [so], I would have told you. I go to prepare a place for you. (3) And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, [there] ye may be also.”
Was Jesus going to prepare a place, then leaving it vacant return to earth, or was the “earth”, same word translated “land”, and literally means arable land talking about a “place” in heaven?
And in Revelation 5:10 where was John when he saw this vision of them who he mad a “kingdom and priests”?
(Rev 4:1 KJV) – “(1) After this I looked, and, behold, a door [was] opened in heaven: and the first voice which I heard [was] as it were of a trumpet talking with me; which said, Come up hither, and I will shew thee things which must be hereafter.”
The “earth” is a reference to the “land” in heaven where John was seeing the Lamb, not on this “land” we are in today.