Call recording is a bit of a thorny issue when it comes to privacy. There are also different rules in different places, making it hard for Google to implement a standard in Android without falling foul of the law in certain jurisdictions. Android's official call recording API was removed in Android 6.0 Marshmallow, so third-party app developers have had to be creative since then. As of Android 9 Pie, it looks like Google has put a stop to it altogether.
As reported by PiunikaWeb, the developers of two well-known call recording apps have said it will no longer be possible without root in the latest version of Android. The maker of Call Recorder - ACR posted a detailed forum entry informing users of the bad news, stating that no third-party apps will be able to offer the functionality going forward. Call Recorder developer BoldBeast echoed this, adding that "root is the only way to go."
To meet the requirements of Vodafone in Germany, where two-party consent is required for call recording, Google was said to be working on a special tone that would play every 15 seconds, thus informing the recipient. It was also rumored that Android Pie would include native call recording, but neither has come to fruition.
Perhaps native recording is something we'll get in 9.1 or with the release of the Pixel 3 — we'll just have to wait and see. In the meantime, you might have to resort to an old-fashioned method involving the loudspeaker function and a recording app. Or why not go even further and dust off your old dictaphone.