[KevinH]

I even tried skipping the loader completely and directly loading Hyphenopoly.js and got the following error in the Javascript Console:

Debug: Javascript error: QWebEnginePage::ErrorMessageLevel "Uncaught ReferenceError: Hyphenopoly is not defined on line:61

Source:sigil:///Users/kbhend/Library/Application%20Support/sigil-ebook/sigil/workspace/Sigil-BxImZW/OEBPS/Misc/Hyphenopoly.js"

So the Hyphenopoly object itself is undefined. It is almost if the javascript version was for a different release than what is needed.

Very very strange.

Then as a final test I commented out the loader script itself and the Readium plugin happily hyphenated everthing even with no Hyphenopoly installed.

So I do not think Hyphenopoloy is used/working at all in that sample epub even if Sigil is modified to allow the fetch api in the "sigil" url schemehandler. I will push that one line change to master anyway, in the hopes you can get things to work eventually.

There is no way it is finding the .wasm files with the path generated by the Hyphenopoly_loader.js as it is looking in the wrong place for those files.

The latest QtWebEngine and Electron builds have a built in hyphenator.