Best VPN for FireStick that ACTUALLY has a working kill switch?

I'm using Surfshark right now and the 'Kill Switch' feature on the FireStick app is a total joke. If the VPN disconnects randomly, the stream just keeps playing on my raw ISP connection for a good 10 seconds before it realizes what happened. I got a warning letter from my ISP last month. What VPN app actually cuts the connection instantly on Fire OS?