Microsoft first started offering public previews of its new Chromium-based Edge browser over two months ago. At the time, it was for AMD64 Windows 10 PCs only, but since then, it's expanded to x86 Windows 10 PCs, and to macOS.
Today though, the firm announced that you can now test out the browser on older versions of Windows, including Windows 7, Windows 8, and Windows 8.1. It's only from the Canary channel for now, which means that you'll get daily updates, and things might break. The Dev channel is coming soon. The reason that it took so long is that Microsoft has to get the telemetry working, as it was already fairly easy to take a Windows 10 build and bring it to another OS.
It's interesting that Microsoft is supporting any of its own apps on Windows 8, which hasn't been supported in a few years now. Windows 7 support is also ending pretty soon, in January 2020.
Microsoft noted a couple of known issues with the new build. There's no dark theme support, and no AAD sign-in. Naturally, you can report other bugs you find or file feedback by clicking on the smiley face.
You can download Edge Insider builds for Windows 7 here, or use one of the links below that to go to the Windows 8 or 8.1 downloads. If you go to the Edge Insider site from your PC, it should prompt you to download the build that corresponds to your OS.