Google has made certain changes in the Android Pie (9.0). The end result is that 3rd party call recording apps will not be able to listen to the microphone during a phone call, making the call recording on Nokia phones impossible. A workaround could be to root the device, but since Nokia has not offered bootoader unlocking, rooting is out of scope.
Nokia phones sold globally come with Android One software. Being one of the closet to stock Android, the operating system does not come with any added enhancements or OEM bloat. Long story short, a call recorder is not built into Nokia phones and a 3rd party app will not work on Android Pie. So, it is probably about time that Nokia starts offering a self developed recording app with its phones. I’m not sure if Google prohibits any such addition under the Android One terms.
Google should also look up at the situation and do something. There can be various situations, legal or other wherein recording a phone call is important.
Just for a mention, Nokia phones sold in China do come with a recorder app and also a in-call UI to handle call recording. They just need to make a similar setup or simply offer a call recording as a System app, allowing it to get the required access to microphone during the calls.
Developer behind the call recording app – ACR has gone into a bit of detail about the situation and what users can do. So, follow his informative piece right here.