Solved! Go to Solution.
Hit the Home Button and then go back into Settings and scroll to the bottom and you will find a new selection labeled Developers Settings
PRACTICE CAUTION [in this area only make changes to settings you know and understand the outcome of]
You'll want to go through the list until you find the option to ALLOW DOWNLOADS FROM UNKNOWN SOURCES and turn it on.
Now you are able to sideload apps not available to you from Googles Playstore
Head over to APKMIRROR and download the Samsung TV+ apk and install it.
Here is a version for the A10e but it might be the same version needed for your S9+ (worth a shot and save you having to download from apkmirror if so) Hope This Helps.
Samsung TV Plus is supported in P OS (Android 9) or above.
The OS of your device may be O OS (Android 8).
If you upgrade your device to latest version, you can install Samsung TV Plus via Galaxy Store or Play Store.