Despite the claims of some illiterate devil worshipers, Anton LaVey was an atheist. Meaning, he did not believe deities to exist. That includes Satan as an actual deity. There are multiple, independent sources where he states this position. You can read many of these in the article “What, The Devil?” at https://www.churchofsatan.com/what-the-devil/ .
An additional quote, from 1971, from his “Letters from the Devil” column: “The Satanist fully recognizes that Satan is nothing more than a symbolic entity representing man himself; his carnal and physical desires, his freedom from enshackling doctrines, and his intellectual capacity to reject those elements of man-made law which prevent him from engaging in life to the fullest. To suppose that Satan is a substitute for the Christian “God” is entirely erroneous. Man himself is the God; Satan is merely the symbolic representation of the WHOLE man and is given a place in Satanic ritual as a strengthening device to affirm one’s own convictions.”
The topic of atheism and non-theistic religions is also thoroughly covered in Satansplain #016:
In summary, people claiming to be “Theistic LaVeyan Satanists” seemingly can’t read, or at least lack the mental capacity to comprehend metaphors. Anybody claiming that Anton LaVey “really” believed in a literal Satan and that the Church of Satan’s position somehow changed later, is simply lying. Don’t take my word for it; look at the documented evidence instead of going by hearsay or by poetic waxing misread by people who can barely type.