Was salvation available to Lucifer and those angels who rebelled with him?

We know that people were created as lesser beings than angels:

What is man that You are mindful of him,
And the son of man that You visit him?
For You have made him a little lower than the angels,
And You have crowned him with glory and honor.
— Psalms 8:4–5 (NKJV)

Paul refers to this psalm and says:

For He has not put the world to come, of which we speak, in subjection to angels.
…
You have put all things in subjection under his feet.”
For in that He put all in subjection under him,
He left nothing that is not put under him.
But now we do not yet see all things put under him.
— Hebrews 2:5,8

Mankind, which included the incarnate Jesus, is still lower than the angels and has not yet received "all things".

But, the promise still stands, as described in the book of Hebrews (these are selections, but one should read it all):

Inasmuch then as the children have partaken of flesh and blood, He Himself likewise shared in the same, that through death He might destroy him who had the power of death, that is, the devil, and release those who through fear of death were all their lifetime subject to bondage. For indeed He does not give aid to angels, but He does give aid to the seed of Abraham.
— Hebrews 2:14–16

Therefore, since a promise remains of entering His rest, … .
— Hebrews 4:1

For you have need of endurance, so that after you have done the will of God, you may receive the promise
— Hebrews 10:36

These all died in faith, not having received the promises, but having seen them afar off were assured of them, embraced them and confessed that they were strangers and pilgrims on the earth.
— Hebrews 11:13

Therefore, since we are receiving a kingdom which cannot be shaken, let us have grace, by which we may serve God acceptably with reverence and godly fear.
— Hebrews 12:28

God has promised salvation to mankind, not to the angels. And when mankind have received that immortality, they will no longer be lower than the angels, but higher:

Do you not know that the saints will judge the world? And if the world will be judged by you, are you unworthy to judge the smallest matters? Do you not know that we shall judge angels? How much more, things that pertain to this life?
— 1 Corinthians 6:2–3

The ultimate purpose of mankind is to become God's family, with Jesus as the eldest son.

And we know that all things work together for good to those who love God, to those who are the called according to His purpose. For whom He foreknew, He also predestined to be conformed to the image of His Son, that He might be the firstborn among many brethren.
— Romans 8:28,29

I will be a Father to you, And you shall be My sons and daughters, Says the LORD Almighty
— 2 Corinthians 6:18

He who overcomes shall inherit all things, and I will be his God and he shall be My son.
— Revelation 21:7

Angels may have a form of immortality, but they will never be God's children, and that is what salvation is all about.

St. Alphonsus di Liguori considers the reprobation of Satan in his booklet Treatiste on Prayer. He concludes that before he fell, he was given sufficient grace by means of prayer to be numbered among the elect angels, but by refusing to start praying or persevere in it, the grace was not turned efficacious.

St. Alphonsus di Liguori concludes that anyone who prays regularly, daily, and frequently will surely receive efficacious grace and anyone who neglects to pray will receive only sufficient grace. This is reflected in Hebrews: "And without faith it is impossible to please God, for whoever would approach him must believe that he exists and that he rewards those who seek him." (Hebrews 11:6)