This doesn't say that Christ's reign ends; it says that Christ rules by forcing his enemies under His feet until He hands the kingdom over to God. The Bible specifically says that Jesus' kingdom will have no end, Luke 1:33. This is one of many evidences that /eis ton aionas/ actually does mean "forever" in normal use. In fact, it means that even in secular documents; Plato uses it as such.
Christ's reign ends:
1 Corinthians 15:25 For he must reign, till he hath put all enemies under his feet.
Therefore He reigns, not forever, but for the eons:
Luke 1:33 He shall reign over the house of Jacob for the eons.
Therefore "for the eons" is not eternal, but temporary & has an end.
Christ gives up the kingdom to God:
1 Corinthians 15:24a Then cometh the end, when He shall have delivered up the kingdom to God, even the Father
What is "of" His kingdom [that is, the fruits of it] shall have no end:
Luke 1:33 and of his kingdom there shall be no end
Eventually all, including Christ, become subject to God:
1 Cor.15:28 And when all things shall be subject unto him, then shall the Son also himself be subject unto him that put all things under him
The result of this is God becoming "all in all" (1 Cor.15:28), referring to universal salvation:
1 Cor.15:28 And when all things shall be subject unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.
"To say that "all in all" signifies "the manifestation of God's supremacy"...is very far indeed from the truth...When we say "Christ is my all," what do we mean? That He is our Lord? Yes, and our Saviour and Friend and our Lover, our Wisdom and our Righteousness, and our Holiness--He is everything to us!...And that is just what God wishes to be and what He will be!...Will He be this only in some? No! He will be All in all!...we have said that when the last enemy [death] is abolished, then the Son abdicates and God becomes All in all. If there were still enmity we might imagine God being over all, but with all enmity gone, it is easy to see how He can become All in all...The "kingdom" is given up to the Father, after all sovereignty and authority and power have been abrogated. What kind of a "supremacy" will God "fully manifest" which has no power, no authority, no sovereignty? Thank God, all these elements, which characterized government during the eons, will be utterly unnecessary when the Son of God is finished with His "mediatorial" work. Instead of God's supremacy being fully manifested at that time, it will be entirely absent, and God, as Father, will guide His family by the sweet constraint of love."
1 Cor.15:22 For even as, in Adam, all are dying, thus also, in Christ, shall all be vivified." 23 Yet each in his own class: the Firstfruit, Christ; thereupon those who are Christ's in His presence;" 24 thereafter the consummation, whenever He may be giving up the kingdom to His God and Father, whenever He should be nullifying all sovereignty and all authority and power." 25 For He must be reigning until He should be placing all His enemies under His feet. 26 The last enemy is being abolished: death. 27 For He subjects all under His feet. Now whenever He may be saying that all is subject, it is evident that it is outside of Him Who subjects all to Him." 28 Now, whenever all may be subjected to Him, then the Son Himself also shall be subjected to Him Who subjects all to Him, that God may be All in all.)" (CLV)
God will be all in all, and everything will be submitted to God; but you missed that Christ reaches this stage by destroying all authorities, including death.
The abolishing of death means an end to the death of those in the second death, which means their resurrection "in Christ" as per 1 Cor.15:22-28.
And the seventh messenger did sound, and there came great voices in the heaven, saying, 'The kingdoms of the world did become those of our Lord and of His Christ, and he shall reign into the ages of the ages!' (Rev.11:15)
9 And a third angel followed them, calling in loud a voice, “If anyone worships the beast and its image, and receives its mark on his forehead or hand, 10 he too will drink the wine of God’s anger, poured undiluted into the cup of His wrath. And he will be tormented in fire and brimstone in the presence of the holy angels and of the Lamb. And the smoke of their torment goes up into the ages of ages, and they have no respite day and night who do homage to the beast and to its image, and if any one receive the mark of its name. (Rev.14:9-11)
20 And the beast was taken, and with him the false prophet that wrought miracles before him, with which he deceived them that had received the mark of the beast, and them that worshipped his image. These both were cast alive into a lake of fire burning with brimstone. (Rev.19:20)
and the Devil, who is leading them astray, was cast into the lake of fire and brimstone, where are the beast and the false prophet, and they shall be tormented day and night -- into the ages of the ages. (Rev.20:10)
3No longer will there be any curse. The throne of God and of the Lamb will be within the city, and His servants will worship Him. 4 They will see His face, and His name will be on their foreheads. 5 And night shall not be any more, and no need of a lamp, and light of the sun; for the Lord God shall shine upon them, and they shall reign into the ages of ages. (Rev.22:3-5)
The verses above indicate Christ & the saints shall be reigning "into the ages of the ages", including the millenial age & the age when the lake of fire (= the 2nd death) is abolished. But 1 Cor.15:25 says Christ's reign is UNTIL He has put all enemies under His feet. Since He is still reigning at the time of Revelation 20-22, all enemies are not yet under His feet. So neither is God yet "All in all" (1 Cor.15:28) nor is death [e.g. 2nd death] abolished yet.
So death is not abolished (1 Cor.15:26), since that is associated with the end of Christ's reign (v.25) & will not happen till He quits reigning. Also those humans who died a second death in the lake of fire, which is the second death, are still dead, so death is not yet abolished (v.26). As long as the second death remains & is not abolished, death is not abolished as per v.26.
Neither is "all rule and authority and power" yet nullified (1 Cor.15:24) by Revelation 21-22. There are still kings in the earth (Rev.21:24). There is still the throne of the Lamb & the saints reigning (22:3,5). So neither is death abolished or God "all in all" (1 Cor.15:28).
God cannot be "all in all" (1 Cor.15:28) while there are still those in the second death & those being tormented in the lake of fire (Rev.14:9-11; 19:20; 20:10).
In Revelation 22:2 we also have leaves that are for the healing of the nations. Who at this time would need healing?
Eventually God will be making all new (Rev.21:5) & will be "in all" (1 Cor.15:28).
And every creature which is in the heaven and upon the earth and under the earth, and those that are upon the sea, and all things in them, heard I saying, To him that sits upon the throne, and to the Lamb, blessing, and honour, and glory, and might, into the ages of ages.(Rev.5:13)
https://www.tentmaker.org/books/hope_beyond_hell.pdf