After dancing with a tambourine, I managed to solve the problem as follows.
Find the file: consentform.html
and replace the top line with the same extended one:
<meta name = "viewport" content = "viewport-fit = cover, initial-scale = 1, maximum-scale = 1, user-scalable = no, width = device-width">
Find the second file: CDVWKWebViewEngine.m
Add code to Cordova-wkwebview-engine \ SRC \ IOS \ CDVWKWebViewEngine.m between line 99-100,
// re-create WKWebView, since we need to update configuration
WKWebView * wkWebView = [[WKWebView alloc] initWithFrame: self.engineWebView.frame configuration: configuration];
// add begin
#if __IPHONE_OS_VERSION_MAX_ALLOWED> = 110000
if (@available (iOS 11.0, *)) {
[wkWebView.scrollView setContentInsetAdjustmentBehavior: UIScrollViewContentInsetAdjustmentNever];
}
#endif
// add end
wkWebView.UIDelegate = self.uiDelegate;
self.engineWebView = wkWebView;
* - 99 is deleted as it duplicates the first line of this code.