Ephesians 5:11 and Acts 26:18, use
σκοτος skotos {skot'-os} from the base of 4639; TDNT - 7:423,1049; n n AV - darkness 32; 32 1) darkness 1a) of night darkness 1b) of darkened eyesight or blindness 2) metaph. 2a) of ignorance respecting divine things and human duties, and the accompanying ungodliness and immorality, together with their consequent misery in hell 2b) persons in whom darkness becomes visible and holds sway
Your mistake is thinking that is cognate to the Hebrew words for darkness
We start with the first darkness mentioned
Genesis 1:2
" And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters "
חשך choshek {kho-shek'} from 2821, - darkness ,dark ,obscurity ,night ,darkness , obscurity ,darkness ,secret place
Nothing about Satan there......
Then, we find a different " darkness " in the narrative:
Genesis 15:12
" And when the sun was going down, a deep sleep fell upon Abram; and, lo, an horror of great darkness fell upon him "
חשכה chashekah {khash-ay-kaw'} or חשכה chashekah {khash-ay-kaw'} from 2821; TWOT - 769c; n f AV - darkness 5; 5 1) darkness
Both חשך choshek and חשכה chashekah are from 2821
חשך chashak {khaw-shak'} a primitive root; TWOT - - darken , dark , blacker , darkness , dim , , variant ; to be or become dark, grow dim, be darkened, be black, be hidden, to be or grow dark, to have a dark color , to grow dim , to make dark, cause to be dark, to hide, conceal,to obscure, confuse (figurative)
( See the Akkadian adaru , to grow dark, gloomy, cognate to Hebrew Adar, when the Moon grows dark, or red in the event of a lunar eclipse AKA " Blood Moon " )
Then, there is
Exodus 20:21
" And the people stood afar off, and Moses drew near unto the thick darkness where God was "
ערפל `araphel {ar-aw-fel'} probably from 6201; TWOT - 1701b; n m AV - thick darkness 8, darkness 3, gross darkness 2, dark cloud 1, dark 1; 15 1) cloud, heavy or dark cloud, darkness, gross darkness, thick darkness
No Satan there
Then there is
Joshua 24:7
And when they cried unto the LORD, he put darkness between you and the Egyptians, and brought the sea upon them, and covered them; and your eyes have seen what I have done in Egypt: and ye dwelt in the wilderness a long season.
מאפל ma'aphel {mah-af-ale'} from the same as 651; TWOT - 145e; n m AV - darkness 1; 1 1) darkness
from
אפל 'aphel {aw-fale'} from an unused root meaning to set as the sun; , - very dark; gloomy, dark
( See The Akkadian adaru and Hebrew cognate, again )
No Satan there...
There is also
Job 12:22
He discovereth deep things out of darkness, and bringeth out to light the shadow of death
צלמות tsalmaveth {tsal-maw'-veth} from 06738 and 04194; TWOT - 1921b; n m AV - shadow of death 18; 18 1) death-shadow, deep shadow, deep darkness, shadow of death 1a) death-shadow 1b) death-shadow, deep shadow, darkness 1c) death-shadow (of distress, extreme danger) (fig) 1d) death-shadow (of place of the dead) (fig)
6378
פך pak {pak} from 6379; TWOT - 1767a; n m AV - box 2, vial 1; 3 1) vial, flask
פכה pakah {paw-kaw'} a primitive root; TWOT - 1767b; v AV - ran out 1; 1 1) to trickle, pour 1a) (Piel) to trickle, drop down (water)
4194
מות maveth {maw'-veth} from 04191; TWOT - 1169a; n m AV - death 128, die 22, dead 8, deadly 1, slay 1; 160 1) death, dying, Death (personified), realm of the dead 1a) death 1b) death by violence (as a penalty) 1c) state of death, place of death
No Satan there
Psalm 88:6 Thou hast laid me in the lowest pit, in darkness, in the deeps.
מחשך machshak {makh-shawk'} from 2821; TWOT - 769d; n m AV - darkness 4, dark places 2, dark 1; 7 1) dark place, darkness, secrecy 1a) hiding-place 1b) dark region 1c) grave
חשך chashak {khaw-shak'} a primitive root; TWOT - - darken , dark , blacker , darkness , dim , , variant ; to be or become dark, grow dim, be darkened, be black, be hidden, to be or grow dark, to have a dark color , to grow dim , to make dark, cause to be dark, to hide, conceal,to obscure, confuse (figurative)
אפל 'ophel {o'fel} from the same as 0651; TWOT - 145a; n m AV - darkness 7, privily 1, obscurity 1; 9 1) darkness, gloom 2) spiritual unreceptivity, calamity (fig.)
from
אפל 'aphel {aw-fale'} from an unused root meaning to set as the sun; , - very dark; gloomy, dark ( See adaru )
And again, no Satan or devil
Now, I could do all 140 + verses, and we would all see that this false dichotomy is based on nothing more than scriptural ignorance, and that the topic is nowhere near as black and white as people would like to claim as
Satan = darkness and God = light
In fact, I bet you've missed some very crucial things by simply thinking that's true, because it's certainly not what the scriptures support