According to Hebrews 1:3, the Son is a “representation” (NASB) of God’s hypostasis.
When the letter to the Hebrews was written, hypostasis and ousia had pretty well the same meaning; both meant a distinct reality, namely, the Foundational Reality which supports all else (God). (Ousia did not mean "substance.") (See, Synonyms)
So, what Hebrews 1:3 means is that the Son is a “representation” of God’s ‘being’. That is how the NIV, for example, translates this verse. Some translations render hypostasis here as “substance.” But most translations interpret this verse as saying that the Son is a representation of God’s “nature.” (See Biblehub)
These three terms have different meanings. They may overlap in meaning, but they are not equivalent. One cannot say, for example, that the Son was begotten from the nature of God, but you can say that the Son was begotten from God's substance, as in the Nicene Creed. So, substance has a corporeal implication which nature does not have.
It is possible to say that the Son was begotten from the being of God. That is something which some of the so-called Arians admitted, but they were not willing to say that the Son was begotten from the "substance" of God for fear of material implications. So, “being” and “substance” are also not equivalent.
“Substance” may be understood in a non-material sense but it also has a possible materialistic connotation; the other two terms do not.
I cannot see a justification for translating hypostasis here as “substance.” I am not aware of anyone, at the time that the letter was written or before, who referred to God’s substance, as we use the term today. The second-century Gnostics used homoousios in that sense. The Nicene Creed says that, since He is begotten from the substance of God, He is of the same substance (homoousios). That makes it abundantly clear that substance is used in the Creed in a corporeal sense.
So, my question is, what justification do translations such as the Berean Literal Bible, the ASV, and the ERV have for translation hypostasis here as "substance?"