The standard messaging app not good enough? Samsung leaves the choice of the standard messaging (SMS) app to its users.

Note: If a screen lock is set and the Samsung device is restarted, the messaging app will not load until the device is unlocked (applies to all apps except the pre-installed messaging app).

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Apps
Step 3:  Open the  menu
Step 4:  Tap on  Default apps
Step 5:  Tap on  SMS app
Step 6:  Choose desired  SMS app
  1. Open the Settings
  2. Tap on Apps
  3. Open the menu
  4. Tap on Default apps
  5. Tap on SMS app
  6. Choose desired SMS app

Samsung Instructions