Caroline

the contention that Hebrew Satan is derived from or the same as Egyptian
Seth is the view of the Temple of Seth and before them is found in the works
of Kenneth Grant.

See for example this from Storm website - which seems to summarise the
argument:

4. On the Satanic Fallacy	(From Storm website)

News Flash: Seth is not Satan. We repeat: Seth is not Satan. (P.S.: Seth isn
’t a Platonic Ideal, Cthulhu, your “Higher Self”, the Prince of Darkness, or
the Dark Side of the Force, either, but let’s concentrate on one thing at a
time.)  The notoriously fantasy-prone Kenneth Grant and Michael Aquino
conjecture that Seth is just another name for Satan, but all historical and
metaphysical evidence refutes their claims. . . .

It’s undeniable that the Catholic Church, influenced by Egyptian Coptic
Christians, gave their concocted bogeyman the Devil some of the attributes
of Seth-Typhon familiar to ancient peoples. But as the Church created its
patchwork quilt symbol of dualistic evil, it drew on the attributes of
hundreds of heathen gods as part of their campaign to demonize all
pre-Christian religions. Therefore, the most one can say is that the
Christian Satan figure was influenced by memories of Seth. Since the Satan
idea was equally shaped by bits and pieces borrowed from many other deities,
this is a far cry from accepting the simplistic equation Seth = Satan.
Seth’s religious cult stretches back thousands of years. His devotees
through the millennia have left an objective, consistent and detailed record
of His specific nature and forms of worship, which the Storm has revived in
terms suitable for today. “Satan” is little more than a loosely-constructed
literary figure whose very lack of substance has made for a convenient
screen upon which any number of fantasies can be projected.

Ironically, in light of the frequent confusion of Seth and Satan in occult
circles, the Storm’s research suggests that there are many more reasons to
believe that Jehovah, the thundering and wrathful donkey-headed desert war
god, was actually a regional form of Seth. We’ve pointed out elsewhere that
there are intriguing Sethian undercurrents in the mythologies of the
Egyptian-trained magicians Christ and Moses, and even within Islam.
Scholarship demonstrates the strong influence Egyptian theology exerted on
the Bible, so it shouldn’t be surprising that traces of the Sethian cult
left their mark on the scriptures. . . .