At English Wikisource, there was a discussion from a new user about the ability to download our (completed) works in the EPUB format and potentially others. After a couple of leads, and some reading I see [[mw:Extension:EPubExport]] is listed as possibly having the capability. Is there a means to test the extension for capability and suitability? Is this something that WMF has a sandbox to test the implementation?
On earlier asking there has been some discussion about it being part Extension:Collection, looking at that page, it refers to the above extension.