"extension permission to use this extension type"
The process of getting permission to use the appx extension type (which seems to be required in order to publish an edge extension) is blocked by Microsoft. It is unclear why I don't get permission and I didn't receive any response on my questions for about three weeks now. My customers are waiting however and I did pay Microsoft so I do expect support to get the extension published.
My extensions store ID is 9P16GP71KWZT.
The chrome version of the extension is available in the chrome store.