WinAppDriver: Appium Dotnet 5.0.0-beta01: Cannot instantiate WIndowsDriver: AppiumOptions "Vendor Prefix" causing driver instantiation error

I was trying out the Appium 5.0.0 Beta01. My capabilities/options looked like this:

            var options = new AppiumOptions();
            options.AddAdditionalCapability("app", "root");
            options.AddAdditionalCapability("ms:experimental-webdriver", true);

            WindowsDriver driver = new WindowsDriver(new Uri(WinAppDriverUrl), options, TimeSpan.FromSeconds(60));

but this set of options, specifically the option for (“app”, "root), threw this error: There is already an option for the appium:app capability. Please use the Application property instead. Parameter name: capabilityName

so I replaced it with this property instead: options.App = "root"; which apparently passes the capability as (“appiumoption:app”,“root”) instead of the old (“app”, “root”) key-value pair. and so now I get this errorr: OpenQA.Selenium.WebDriverArgumentException: Bad capabilities. Specify either app or appTopLevelWindow to create a session

I looked into the Appium dotnet source code and looks like the AppiumOptions class’s method to create a new AppiumOption has been modified: AppiumOptions.cs diff: Appium 4.3.1 vs 5.0.0 Beta01 This method in particular seems to have brought the change, adding a vendor prefix before any and all additional options/capabilities:

public void AddAdditionalAppiumOption(string optionName, object optionValue)
        {
            string name = optionName.Contains(":") ? optionName : $"{VendorPrefix}:{optionName}";
            this.ValidateCapabilityName(name);
            this.additionalAppiumOptions[name] = optionValue;
        }

I couldn’t find any way to get around it. Here’s a ticket for this issue in the Appium Dotnet Repo: https://github.com/appium/appium-dotnet-driver/issues/487

@kat-y @DHowett Is this being taken care of for the next release? This is a blocker on the upgrade path to Selenium 4 and Appium 5.