Do actual prophets exist on the earth today?
How do we know if they're not just making things up?
You may say to yourselves, "How can we know when a message has not been spoken by the LORD?" If what a prophet proclaims in the name of the LORD does not take place or come true, that is a message the LORD has not spoken. That prophet has spoken presumptuously. Do not be afraid of him.
In the past God spoke to our ancestors through the prophets at many times and in various ways, but in these last days he has spoken to us by his Son, whom he appointed heir of all things, and through whom also he made the universe.
Hebrews is referring to if prophets exist/are needed. The Deuteronomy verse refers to know they're not making things up.