Just to clarify, WebSQL was not available in WkWebView on IOS9 and early betas of IOS10, but is avaliable in all current versions of IOS10/11 and works well. In fact, an alternative to using this plugin on ios may be to use my slightly hacked version of the ionic wkwebview code (https://github.com/mzealey/cordova-plugin-ionic-webview) which just implements wkwebview on ios10 and higher. This works fine for a WebSQL-heavy project with many users that I develop.
Just to clarify, WebSQL was not available in WkWebView on IOS9 and early betas of IOS10, but is avaliable in all current versions of IOS10/11 and works well. In fact, an alternative to using this plugin on ios may be to use my slightly hacked version of the ionic wkwebview code (https://github.com/mzealey/cordova-plugin-ionic-webview) which just implements wkwebview on ios10 and higher. This works fine for a WebSQL-heavy project with many users that I develop.