I have always used a local web page of my own making to use as a home page. The new web extensions version did not on first glance appear to support the ability to use anything other than http:// or https://. On closer examination it turns out I can use my local web page - just read the instructions carefully. Just select "Local File" and "Load Local File" and you've solved the problem. I think if I were the author I'd make this instruction a little more plain.

I've used this extension for years with nothing but good things to say about it.