So rejection being pushed back to December 2020 was obviously a lie by Apple.
ITMS-90809: Deprecated API Usage - New apps that use UIWebView are no longer accepted. Instead, use WKWebView for improved security and reliability.
I’ve read the other warning threads. The app uses only two plugins, SplashScreen and QR Scanner. The latter doesn’t use UIWebView. No Appodeal or ads at all.
Before I on a hunch update Corona SDK and therefore also XCode and therefore also OSX version with GB of download and backup first at hours of cost to my employer: Will updating to the latest Corona version fix this? (In other words, was this ITMS code addressed in a recent build.)