As with the ringtone, the notification tone for the SIM cards can be set independently of each other; in addition to many standard tones, no separate notification tone can be added on the Samsung device.

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Sounds and vibration
Step 3:  Tap on  Notification sound
Step 4:  Choose desired  SIM-Card
Step 5:  Choose desired  notification sound
  1. Open the Settings
  2. Tap on Sounds and vibration
  3. Tap on Notification sound
  4. Choose desired SIM-Card
  5. Choose desired notification sound

Samsung Instructions