I just bought a Samsung Galaxy S8+. Everything is working great, but there is one little thing I can't seem to figure out and that is the ringtone uses only the speakers.
Can I route the ringtone through a headset when it is connected?
Sadly there's no way to do that presently. There's a very old question here that tried achieving it in Android 2.2. You can try setting up Tasker to do it for you. Android doesn't have anything built in for this as far I know.
Did you ever resolve your question? It appears that Samsung Sound Assistant can do what you want.
However, you might want to check my question about this - just so you are aware of the problem I am having.