The Strava Wear app will become available for the new Samsung Galaxy Watch 4 running Wear OS 3.0; over the next few days. Please keep an eye on the Wear Play Store for the ability to download the Strava Wear app.
Please be aware that we do not advise running Strava and other workout apps simultaneously on Wear OS devices. Other workout apps that record active exercises may interfere with your recording. The app you started most recently should end the previously running app. There is a platform update coming next week that will improve the experience of switching between 2 workout apps. In the future, your Strava activity will always be ended and saved if you start another exercise tracker after starting Strava. And, you will be able to start a Strava exercise when another workout is in progress (but note that this will end the other app's tracking).
More information on the Wear OS app can be found here.