Although these are only the first preview builds to reach the public, those interested in trying Edge on Windows 7 and 8/8.1 can finally do so. Microsoft Edge now uses a Chromium core, the same that can be found inside Google Chrome, Vivaldi, Brave, and Opera. The downloads are available on the official Microsoft Edge Insider website.
https://www.notebookcheck.net/Chromium-based-Microsoft-Edge-for-Windows-7-and-8-1-now-available-for-download.424852.0.html