Same problem here - for me its either the unknown error or an unknown error + variable DX errors.

Ive tried everything you tried and more, but i crash regularly after only a couple minutes. At this point i can safely say ive done everything i can, but i just cannot play the game anymore.
It all started with Endwalker for me. I had the occasional crash every other week before, but they just became more and more frequent after the EW launch.
Very very frustrating!
I wish they'd specifically comment on this better sooner than later, spent the whole last week checking my hardware and software for possible problems - even contacted my GPU vendor.
But since FF is the only game crashing, i can safely say its not a fault on my end.