You can set different ringtones for the two SIM cards to quickly identify which card the incoming call comes from.
Setting Path:
realme UI 1.0 and above versions: Google dialer > Settings > Sound and Vibration > Ringtone > Select the ringtone for SIM card 1/Card 2.
realme UI R & T & S & Go & U edition: Settings > Sound & vibration > Phone ringtone SIM1/SIM2 > Choose System Ringtones/Add ringtones.