Trying to run mobile web tests for iOS, but getting WebDriverException: Message: An unknown server-side error occurred while processing the command. Original error: Could not navigate to webview; there are none!

Tests are failing initially when initializing driver with the following capabilities:

{“udid”: …, “deviceName”: “QA iPhone 7 Plus”, “platformName”: “iOS”, “platformVersion”: “12.2”, “browserName”: “Safari”}.

The underlying exception is: WebDriverException: Message: An unknown server-side error occurred while processing the command. Original error: Could not navigate to webview; there are none!

I do see that the Safari browser launches, but nothing else.

I started getting this when updating to the latest Appium (1.12.1) and iOS version (12.2).