Ever since public testing began on Microsoft's new Chromium-based Edge browser, it's only been available through Canary and Dev channels, which are updated daily and weekly, respectively. The Beta channel, which will be updated every six weeks, has been shown as 'coming soon' since day one.
While Edge Beta leaked for Windows back in May, today, it was actually leaked for Mac by infamous Microsoft leakster WalkingCat.
Of course, if you're looking for the stability that will come from the Beta channel, this is not it. There's a reason that Microsoft hasn't released this yet. The firm is testing updates through the various channels, so there are most certainly Beta builds, but they're not the same Beta quality that you'd get if they were open to the public. If you install this on your Mac, all you're getting is the new 'Beta' banner across the Edge logo.
Microsoft's Chromium-based Edge browser has seen no shortage of leaks in its short lifetime, starting with a couple of weeks before it was available to the public. The original Canary and Dev builds for macOS were leaked ahead of time as well. It's probably safe to assume that there will be more leaks on the way.