Isn't there an old interpretation of the Bible that stated Satan & Lucifer weren't the same guy & that Satan was actually God's friend?
That sounds a bit like Gnosticism (the belief that Satan created the physical world and is equal to God), but I'm not sure.
There's a lot of different variations on Gnosticism, and since Gnostism was labelled a far-right hate group and deplatformed for a couple thousand years, there's both a) little information on the beliefs and practices of any specific gnostic sect, and b) no single governing body that arose and declared what gnosticism canonically "was".
That said - yes, sort of.
Gnosticism is basically The Matrix as a religion. Gnostics share a common belief that the physical world around us - the carnal world of the senses - is in some sense "false". It's an illussion, maybe even a prison, maybe even hell. Gnostics further assert that there is another world - a higher, spiritual world, a world of truth and beauty and purity - which is normally hidden from us, but can be made accessible if you have the proper knowledge (or "gnosis").
Picture yourself on Reddit. You have always been on Reddit. You have never been to any other part of the internet, and you probably don't know that any other part of the internet exists. The Reddit jannies start harassing you; banning your favorites subreddits, giving you warnings because you want to eat food instead of bugs, deleting any thread you make that's even remotely critical of trannies. You start to get this sneaking suspicion that you're living in Clown World; that Reddit is not, in fact, reality, but is in instead some kind miserable, spiteful, passive-aggressive purgatory in which you've somehow become trapped. Eventually, an old, bearded sage comes by, a traveler from New Zealand he says, and he gives unto you a magical formula. He tells you about a thing called a "URL bar", and you discover that you can use this secret knowledge to escape Reddit and cast yourself into a whole new world - an "internet", millions of pages and communities unmoderated by fat, middle-aged trannies who want you to eat bugs.
That's Gnosticism. More or less.
As for Satan; some Gnostics think Satan's a good guy, yes. Many Gnostics believe that the god of the physical world, a being called the Demiurge, is evil. In some traditions, the Demiurge is identified as the God of the Bible, the Jewish God YHWH. The Demiurge is not ACTUALLY "God", as in, God the Ultimate Being, Creator of the Universe - rather, He is an imperfect emanation of the True God, and His main goal in life is to keep normies from ever actually coming to know the True God who resides in the Spiritual/ Gnostic/ Morpheus/ Kiwifarms realm that the Gnostic practitioner is striving to access.
But that then begs the question of, is Satan opposed to the Demiurge? Or is the Demiurge Satan?
A very popular contemporary interpretation is that "the Biblical serpent", or "Lucifer", or "Satan" (who aren't necessarily all the same being) are in fact good guys, master trolls who are trying to fuck with the Demiurge, e.g. by giving Eve the Apple of Knowledge, in hopes of freeing her from the Demiurge's globohomo AI censorship grid. But that's not necessarily how any given trad Gnostic would have viewed the story. It's possible that, for example, the serpent was the Demiurge, and the apple actually imprisoned Eve (and Adam, and all the rest of us poor fuckers) in the Demiurge's anti-Eden "real world". Again, there's no canon Gnosticism, so it's anyone's guess.
