How do I pronounce eta?
In Modern Greek: /i/.
When reading Ancient Greek to myself, still /i/. I’m Greek, which makes me Reuchlinian, as Haggen Kennedy described: I pronounce Ancient Greek as Modern Greek to myself.
When reading Ancient Greek out loud, or describing Ancient Greek historically, I do not use whatever weird-ass Pronunciation of Ancient Greek in teaching they have in these parts. I do what we reasonably think eta originally was: [ɛː].