How can I rephrase: adb shell "pm block com.sec.knox.bridge" to work in an Android 10 phone?
As mentioned by @Firelord, use pm disable --user 0 instead of pm block. pm block is deprecated (not exist of new versions of pm). if you have an error with disable then the application still device admin or the package name is not com.sec.knox.bridge.
Check if the App is device admin
adb shell dumpsys device_policy | grep knox

If the command output a result, then the application still device admin.
To be sure that the package name is com.sec.knox.bridge:
adb shell pm list packages | grep knox