How do I see who else is logged into my account and how do I log them out?

Even having my Roku TVs to Lan from my secure router with Openvpn and Encryted DNS and MAC binding with mobile and device disabled they are causing disconnects.They have wifi hacking devices listening with a 100 mile range doing DOS binding attacks with phones and a laptops.They grab the Roku wifi signal clone the IP having a network bridge to a router and modem having free internet using the Roku IP.A secure network doesn't protect my Roku devices because there is no way to enter a secure DNS.I am replacing my Roku devices with TVs that are secure.