As mentioned earlier, Samsung DeX is no longer supported on Mac. But if you have the older version installed, and it’s not working, you need to allow certain permissions.
On your Mac, go to "System Preferences -> Security and privacy -> General tab." If you see a message that reads “System software from developer DEVGURU Co. was blocked from loading,” click "Allow" under the "Allow apps downloaded from" section.
Also, go to "System Preferences -> Security and privacy -> Privacy tab -> Accessibility." If Samsung DeX doesn’t show up, click on the "+" sign and select "Samsung DeX."