But it's hard to talk about magic without invoking religion.
This reminds my of the approach I took in my old 3e homebrew setting. All "magic" was just different, equally valid, and readily-weaponizable belief systems.
One culture's magicians used psychic/psionic powers, which they
claimed were the product of their insights gleaned from their people's migration across different planes of existence towards Paradise.
Another culture had alchemists who used batty, baroque steampunk technology and gleefully pseudo-scientific terminology, which, courtesy of my friend John, often had a wonderfully Vancian ring to it.
Another school of magic exclusively used teleportation gates to create effects. Practitioners viewed this ability as an innate ability shared by all living souls. What they were actually doing was exploiting the path the dead took to the afterlife/God. Since God was omnipresent, by opening a path to His presence they could transit any other point in the material universe.
Yet another bunch were mumbo-jumbo spouting black magicians working for a fallen angel who paid them in the (minor secrets) of the universe.
On a trip to the Land of the Dead the PC's met arms dealers from (nearly) the end of time who mixed traditional fantasy magic with present-day technology and super-science. Which fit them, since the outfit was part evil cult, part Gallifreyian Halliburton/Blackwater, whose employees came from every location and era.
Mainly all of this was an excuse for me to parody the language and conventions of F/SF fiction.