If you study verse 28 of Ezekiel 1 very carefully, the rainbow seems to be what is described as the ‘likeness’ or resemblance of the Glory of God:
28 Like the appearance of the bow that is in the cloud on the day of rain, so was the appearance of the brightness all around.
Such was the appearance of the likeness of the glory of the Lord. And when I saw it, I fell on my face, and I heard the voice of one speaking.
Ezekiel 1:28 ESV
See the Interlinear version as well at: https://biblehub.com/interlinear/ezekiel/1-28.htm which makes this clearer.
When I was writing the article Finding Jesus in the Old Testament the Lord spoke to me about how the Holy Spirit was the Rainbow that God placed in the sky after the flood. Ezekiel 1:28 corroborates what He told me.
In ancient Sumerian literature the fallen angels Inanna and Enlil are referred to as rainbows. In the Sumerian story ‘Inana and Šu-kale-tuda the South wind’ Inanna is said to have stretched herself across the sky like a rainbow and in ‘Enlil in E-Kur’ Enlil is described as spanning the sky as the rainbow.
