Number 4. - Any issues with Edge may self correct (or be exacerbated) when MS updates existing Win 10 users with Edge Chromium. (Download available now for Win 10, 7, 8 and macOS. ) I checked the book TOC in the read-only mode of Learn 3.8 MOOC with Edge Chromium and it displays fine.
Full details re: the Edge Chromium update...
https://www.howtogeek.com/659857/what-you-need-to-know-about-the-new-microsoft-edge-browser/