I think I made a post on this last year, but I want to make it clear again:
The idea that Nicholas Schnee is dead is a work of fanon.
The sum total of the canon information on the fate of Nicholas Schnee is that he retired due to illness, and left the SDC in Jacques’ hands.
That’s it. That’s everything we were given.
If he turns out to be alive over the course of the Atlas Arc, do not call it a retcon. Because it will not be a retcon.
Is it possible he’s dead? Of course it’s possible. But it is not a certainty, nor has it been clearly hinted at.
But the fandom seems to accept his death as a fact, when it is not, and I’m trying to nip the inevitable complaints in the bud.