When God formed the earth, He called it "good" not perfect.
Obviously, evil was already present at the formation, for He put a tree of the knowledge of Good and Evil in the garden.
Do we have such a tree available to modern man?
Are we not all formed and prone to evil and have to be taught good?
Adam did not have to be taught what was good but what was evil - don't eat the fruit of that tree. Was the tree itself evil? Would God have placed evil in the garden?
I do not agree that "privation" is the source of evil.
Lucifer was not in "privation" (lacking full or sufficient) in resources, knowledge, or ability when "evil was found in his heart." Ezekiel 28“You were blameless in your waysSome would use human understanding and have two (perhaps three) conditions that can exist. That which is and that which isn't. For example Pathos (feelings) and the opposite antipathy (anti-pathos - or opposed feelings). One is to consider something good, or evil opposite. The third would be some neutral position residing in the medium.
From the day you were created
Until unrighteousness was found in you."
But, consider the thinking that evil is not a "privation" of good, but a "perversion" of good.
Lucifer took good and claimed it for himself. Certainly, that was depriving God of glorification, but if we follow the thinking of some on the thread - such privation obliges God be considered evil (being deprived of glory) and Lucifer being as good having the glory.
Rather, God remained God, and Lucifer has continued from that time to pervert the truth into a lie.
All good has the ability to be marred by perversion. The earth was good, the garden was good, the wholesomeness of all creation was good, but the good was made perverse - not deprived - it remains that God allows the rain on the just and unjust.
Often we humankind dwell in the thinking of either/or - neither/nor rather than catching a glimpse of better,best, worse, worst.
God gave the law to show what was best and establish that which was not the best.
The OP seeks to discuss "On what grounds can one speak about a past atrocity as being "evil" when it was determined by God for his Glory?"
IMO it is the same issue as what was foundational to the earliest account of evil - perverting good into self adulation.
God determined all for His glory (the heavens declare the glory of God and such other verses) but perversion brings atrocities. Doesn't mean that good does not still exist.
I do not agree that God determined sin would occur. Why then would God be grieved at sin?
Gen 6:6 And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
7 And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
If God desired and determined that sin would occur, then it is nonsensical he would be grieved when his own plan came to pass.