Why is "Your will be done" not redundant?

It's not a matter of us asking for the lord's will but, rather acknowledging him and that his will and not our own be done. In this prayer, we glorify the father and in doing so the father glorifies the son who is in the father, as the prayer itself is provided by the son, through the holy spirit.

The Lord's prayer as our daily statement of purpose and petition for support

My faith tells me that everything happens according to the Lord's will anyway, so why pray asking for this to happen if I believe that this is the only thing that can ever happen in any circumstances anyway?

I know you didn't mean it, but your statement implies fate / destiny, as though we have no role in God's will. But in Christianity we are active participants, God's hands and feet in this world so to speak, in advancing His Kingdom on earth, battling Satan's forces that want to reduce His Kingdom. A believer sees a Christian life as a battleground, as many hymns describe such as Onward Christian Soldiers.

Thus, when we say "Your will be done", it is NOT an intellectual statement about God's sovereignty / power, but it's a soldier's decision to enlist in God's army. The full text is "Your Kingdom come, your will be done, on earth as it is in heaven." God is fully established in heaven, but not yet on earth since Satan is still allowed to operate. By saying that, as a member of God's army we declare our readiness to fight TODAY as well stating our petition for "Give us our daily bread" because we cannot fight on our own resources.

It is as though God asks us in the morning: are you willing to fight for me today? God only asks for willing soldiers, because He respects our free will. By saying "Your Kingdom come, your will be done on earth as it is in heaven" we declare our stance with God, similar to a pledge of allegiance to a country, that "Yes, I'm with you, and I want to fight your cause in the world for the glory of your kingdom on earth."

In doing this we are imitating Jesus at Gethsemane, at the hardest stage of His own battle with evil:

"Father, if you are willing, please take this cup of suffering away from me. Yet I want your will to be done, not mine."

The other 2 elements of the Lord's prayer are also present in Jesus's Gethsemane's passage as well (see Luke 22:39-46): daily bread (angels strengthening Jesus) and dealing with temptation. Jesus had a choice: go with the war plan, or quit. Just as he was successful against Satan's temptation during the 40 day fasting in the desert, he made a decision to align his own will with God's will, relying on God's strengthening. That's the full meaning when we pray the Lord's prayer.

God's will and Our will

OP Comment (emphasis mine)

We make plans, and we change them occasionally. But God knows what we will finally do, in every case. None of our actions can alter His will, this is one of the things I believe most firmly - nobody's actions can prevent the will of God from being done, it is impossible.

Within Christianity there are different models of reconciling God's foreknowledge, our freedom of will (subjectively experienced), and God's providence (which includes various types of God's will). Arminian, Reformed, and Catholic theologies each has their own model resulted from each tradition's various level of human depravity as well as various level of determinism of God's will.

Therefore the statement "None of our actions can alter His will" is not strictly true in the Arminian's view of God's providence which I answered here. In Arminian theology there is a larger role of human's participation in God's plan to the extent that God will work around our free will ! The motto is "God is in charge but not in control."

It's unfortunate that Christianity in the West has degenerated into intellectualism, but if we carefully read the Bible (both OT and NT), God demands an action response, not just intellectual agreement. Human being consists of reason, will, and emotion and it only makes sense that God doesn't want compartmentalization but our full being. Jesus keeps asking "follow me". Paul keeps exhorting "imitate me to be slave of Jesus Christ". James emphasizes "faith without works is dead". All believers are then called to purify our character (with the help of the Holy Spirit) and doing service in the world (with God's grace and opening of doors). So it makes total sense to say the Lord's prayer as a prelude to action, a full human response to God's gift of salvation instead of merely an intellectual statement about God's will.

In Christian theology, God is thought of as expressing His will in more than one way.

This article goes into some of those categories from a Reformed perspective: https://www.monergism.com/discerning-god%E2%80%99s-will-three-wills-god

By quoting Augustine, the previous article draws on Roman Catholic sources, and by quoting John Calvin, the Reformed tradition.

These articles discuss it from a Roman Catholic perspective:

https://spiritualdirection.com/2016/01/25/what-is-gods-will-part-i-of-ii-his-indicative-will

https://spiritualdirection.com/2016/02/01/what-is-gods-will-part-ii-of-ii-his-permissive-will

1) Decretive Will of God. God wills a thing and it happens exactly that way without exception, like creating light, the world, and establishing the laws of nature.

2) Preceptive Will of God. God's published commandments, laws, and moral code. God's will is that no one should steal, but people do steal. God may arrange consequences for that stealing sooner or later, but does not prevent the act.

A Roman Catholic might call this the Indicative Will of God.

Roman Catholic FR. JOHN BARTUNEK says in his article:

"God’s indicative will always flows from his wisdom and his love. In other words, whatever he wants us to do is for our greatest good. In this category we find the Ten Commandments, the commandments of the New Testament, the commandments and teachings of the Church, the responsibilities of our state in life, and specific inspirations of the Holy Spirit. If we want to know God’s will for our lives, those are the places we need to start."

3) Permissive Will of God. God chooses to permit that which offends his Preceptive Will.

Of this, FR. JOHN BARTUNEK, LC in his article says:

"... permissive will, the things he permits to happen without actually commanding them".

and later...

St. Augustine’s short answer is worth mentioning, however. He wrote that if God permits evil, it is only because he knows he can bring out of that evil a greater good. We may not see that greater good right away; we may not see it at all during our earthly journey, in fact. But Christ’s resurrection (Easter Sunday) is the unbreakable and undying promise that God’s omnipotence and wisdom are never trumped by the apparent triumphs of evil and suffering (Good Friday).

So when we pray, "Thy will be done", we are asking that God's Preceptive will be realized in the material world, instead of His permissive will. Sometimes this occurs because we submit our will to His and obey that Preceptive Will (the Ten Commandments, for example). Other times, this is because God exercises His Decretive Will and moves actions that might have been governed by His Permissive will into the category of things finally decided. When God performs a miracle, for example judging the world by flood, all those permissive wills were overruled by one decree.

Why do many Christians believe in such a complex understanding of God's will? Because of this paradox: God is sovereign (His will cannot be opposed), yet humans have free will (whose extent is widely debated, such as in Luther's On the Bondage of the Will, Calvin's doctrine of Total Depravity, etc). A universe in which both of those things exist is not a simple one.