For anyone how is still facing the same issue. This is the solution:

1. Install the plugins,

ionic cordova plugin add cordova-plugin-ibeacon

npm install @ionic-native/ibeacon

2. Modify the following three files in path node_modules/@ionic-native/ibeacon with the ones in the repository ionic5ibeacon

• index.js
• ngx/index.js
• ivy_ngcc/ngx/index.js

The solution has been tested using both iOS and Android devices. see

Thanks IT-Dan