The new Chromium-based Microsoft Edge will impersonate other browsers depending on the site being visited. This may be done for compatibility reasons, like rendering pages or how video will be streamed and played back. Microsoft now uses the Chromium Blink engine instead of it’s original Edge HTML engine. The new browser will switch its user agent to pretend to be a different browser. For certain sites it should impersonate Google Chrome (ChromeUA) or the original Microsoft Edge (EdgeUA) for certain sites.
Source: https://www.bleepingcomputer.com/news/microsoft/the-new-microsoft-edge-sometimes-impersonates-other-browsers-user-agents/