Thanks @Sujan12 . I upgraded the components but the error was still there.
However, I accidentally bumped upon https://forum.ionicframework.com/t/unable-to-use-ionic-cordova-run-android-prod-release/114430/3. This made me create a separate build.json file for the debug/release keystore files and finally, building successfully with command “ionic cordova build android --buildConfig”. Thanks for your help!