We pray that God's will ( His purpose ) be done ' here on Earth ' as it is done in Heaven.
So, when
1 Corinthians 15:26 says 'enemy death' will be destroyed it is talking about Earth.
Yes, it is talking about the enemy, which is spiritual death, which was destroyed on Earth when Christ returned.
Physical death will never be destroyed because God created the human body to be mortal, not immortal.
1 Corinthians 15 says that there are
two different kinds of bodies:
--- The glory of the heavenly bodies is
different from the glory of the earthly bodies.
--- For just as there are natural bodies, there are also spiritual bodies, which are
different.
Our physical bodies cannot inherit the Kingdom of God which is in Heaven. These dying bodies cannot inherit what will last forever is referring to Heaven, which will last forever. Our physical bodies will die and we will be raised (resurrected) as spiritual bodies that will be suited to go to Heaven and live forever.
1 Corinthians 15:40-54 New Living Translation
40 There are also bodies in the heavens and bodies on the earth. The glory of the heavenly bodies is different from the glory of the earthly bodies.
44 They are buried as natural human bodies, but they will be raised as spiritual bodies. For just as there are natural bodies, there are also spiritual bodies.
50 What I am saying, dear brothers and sisters, is that our physical bodies cannot inherit the Kingdom of God. These dying bodies cannot inherit what will last forever.
51 But let me reveal to you a wonderful secret. We will not all die, but we will all be transformed!
54 Then, when our dying bodies have been transformed into bodies that will never die,[
c] this Scripture will be fulfilled: “Death is swallowed up in victory.[
d]
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There is also a New Earth, also referred to as the Kingdom of God on Earth, and that Kingdom will be inhabited by people who are "living" on Earth when that Kingdom is established on Earth.