Sea Breeze there’s a much better case to be made for Jesus being called “god” here than in Acts 20:28, but even so it’s far from clear cut. Some very competent Greek scholars have agreed with the NWT reading here and on the flip side, even if Jesus is called God in this verse it’s obviously in a very qualified sense because 1) it’s quoting a verse where the king of Israel was also “god” in some sense and 2) even as “god” Jesus still has another who is “God” to him in verse 9. In Bible times it was perfectly possible to call other beings, angels and humans, gods in a qualified sense. Given that is the case why would this title be denied to God’s own Son, the most powerful being in existence next to God himself?
The whole argument of Hebrews chapter 1 is that Jesus “has become” better than the angels because he inherited a name greater than theirs. If what the author actually wanted to argue was that Jesus is in fact almighty God himself, then there seems to be a lot of beating about the bush with the angels talk, and specifying the particular ways in which Jesus has become superior to the angels. If Jesus was actually believed to be God almighty then it seems rather redundant to argue he is now superior to the angels.