Can I submit an audiobook even if I don't have an ebook version?

Yes!

You are able to submit an audiobook, even if you don't have a print/ebook edition yet.

The only exception to this is Audible, as they require an ebook/print copy listed on Amazon in order to distribute on Amazon/Audible. If you do not have the print/ebook on Amazon, you would not be able to distribute to Audible and would have to leave them unselected from distribution.

This is the only exception; every other distributor allows for you to upload the audiobook without a print/ebook edition. Additionally, you are able to add Audible as a distributor after the title has been published if you do upload an ebook version to Amazon.