Change default clock app in Samsung Galaxy Note 9
Enable developer options and ADB on your phone, and get platform-tools for your OS. Then run:

adb shell
pm list packages | grep [whatever the app name is]
pm hide [name of package]


Alternatively pm uninstall -k --user 0 [name of package] to remove it completely.

More detailed explanation here: https://www.xda-developers.com/uninstall-carrier-oem-bloatware-without-root-access/