Sabbe dhamma anatta = all phenomena are not self.
Therefore, anything within the domain of experience is not-self.
To affirm or deny the existence of a self/soul/atman beyond the "world" (loka) of experience is inherently speculative, as it is beyond the range of sensory/phenomenal experience. Either metaphysical proposition is unverifiable.
What is important, and of relevance to the pursuit to end dukkha, is that there is no self to be found
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"The uprooting of identity is seen by the noble ones as pleasurable; but this contradicts what the whole world sees." (Snp 3.12)
"To argue with a person who has renounced the use of reason is like administering medicine to the dead" - Thomas Paine