The Big Bang is indeed something from nothing. There is a basic factual condition...in the beginning there MUST have been nothing...an absolute nothing. From that absolute nothing there is everything.
Thats a fact...however you want to paint it.
At the point at which "the big bang exists" is true (there's a reason I'm speaking weirdly; I'll get there), all matter and energy exists at a dimensionless point. No space, no time. That is not "nothing". It's an everything at infinite density. It doesn't fit into human language properly.
So, ok, there is a point at which "there is the big bang" is true.
There is point at which "there is time" is true. It only makes sense to speak in temporal terms
after the point at which "there is time" is true. Speaking of anything else doesn't really work in human language; it only works in mathematics, since there is no temporal relation between the point at which "there is the big bang" is true and the point at which "there is time" is true.
The point being, to say that the big bang "came from" something is a fundamental error. So too is speaking of a "before" the big bang. The concept of
coming from is illogical at points where "there is time" is false. Things like the Hartle-Hawking no boundary proposition were crafted to explain some of this, but they only
sort of translate into human language.
I suspect the "something from nothing" idea relates more to speculative theories regarding what quantum foam in an existing area of space-time might produce
(ie, discrete universes, making discrete universes, making discrete universes, necessarily comprising an infinite set of universes; a set where not only is there a discrete universe for all possible states of all possible energy/matter/etc described by all possible laws of physics, but in fact an infinite number of each specific variation of universe - an infinite number of universes exactly like this one right down to the spin state of every last quark). But, that presupposes an existing quantum foam in which just the right fluctuation must occur. That, too, is not nothing.
https://www.nbcnews.com/mach/science/what-multiverse-ncna876136
Of course, what in fact is the truth depends rather on what the total true physics is. Is string theory right? Is it some other grander theory that encompasses standard field and quantum theories (ie, the sesarch for quantum loop gravity).
It very well may be that the concept of an ultimate beginning is fundamentally wrong, that existence didn't so much 'come from nothing' but rather that the question of 'what did existence come from?' is not a coherent question. There was no "beginning". There is no point at which "there is nothing" is true. Is simply
is. (No doubt a religious person will be tempted to quote "I am that I am").
These are not comfortable ideas for the human mind.