Most of what I’ve seen has been people reusing the existing unified magic system, and even all or most of the standard spells, regardless of what they’re trying to represent.
Is there anything really different out there, for 5e in particular?
There's Aka5hic Mysteries which brings Dreamscarred Press' Akashic Mysteries from PF1 to 5e. (Akashic Mysteries bring 3.5's Magic of Incarnum to PF1 but more balanced.)