Quoting you: “The writer of Hebrews confirmed this in chapter 1, agreeing that when God wants to be visible, He appears as Jesus.”
Here you’ve reminded me of a recent thought I had and would like to hear your opinion. In the old testament, prophets had visions of God sitting on His throne (e.g. Isaiah). Would this have actually been Jesus sitting on the throne in a recognizable bodily form; as we’re taught by Jesus that ‘God is a spirit’ and I presume that He hasn’t got ‘human form’?
I was talking about God wanting to be visible in the physical realm. People who see visions are seeing beyond the physical realm. Therefore they would be able to see God and angels and all kinds of things humans wouldn’t ordinarily be able to see. 2 Kings 6:15-17 is a good example. Elisha’s servant thought they were surrounded by enemy troops and was afraid. But when Elisha prayed that the Lord would “open” the servant’s eyes to the supernatural, he saw the hills full of horses and chariots of fire in far greater number than the enemy troops.
I think Isaiah, Ezekiel, and others who saw visions of the spiritual world were enabled to see beyond the limitations of ordinary human vision, including the ability to see God Himself.