This is fixed by using Microsoft.Edge.SeleniumTools, added in RM-7390.
In an undetermined Version after V79 of MS Edge (Chromium) the support for changing EdgeOptions is broken. (Tested with Edge V84)
E.g. edgeOptions.AddAdditionalCapability ("useAutomationExtension", false);
Maybe the OpenQA library (OpenQA.Selenium.Chrome.ChromeOptions) doesn't directly support Edge after a certain version and the library Microsoft.Edge.SeleniumTools provided by Microsoft should be included instead: https://docs.microsoft.com/en-us/microsoft-edge/webdriver-chromium?tabs=c-sharp#use-selenium-3