The prevailing argument is that the Hebrew word for "day" in Gen 1 is the same as in other places where it's obvious it is to be taken literally. Therefore, you must interpret it as 24 hrs.
To that I say, the word for "lion" in, "Your enemy the devil prowls around like a roaring lion", is the same word used in other places (e.g. David killing a lion)...
Indeed, Hebrew is a rich and poetic language."...And the evening and the morning were the first day."
Evening is the Hebrew 'ereb or dusk
Morning is the Hebrew boqer or dawn
Day is the Hebrew yowm or from sunrise to sunset, or from one sunset to the next
But this doesn't address what, to me, are obvious issues.
1) You didn't address the question of how there can be a "dusk" or "dawn" without a sun.
2) "Dusk" and "dawn" are unrelated, lexicographically, from a literal 24 hour day. Those words describe the setting and rising of a sun, whenever that occurs. Dusk and dawn, while currently timed at a bit more than 24 hrs. here on Earth, does not mean that has always been the case.