Agreed, networking knowledge can be pretty ephemeral if you don’t have a way to put it into practice and solidify that knowledge in your brain.
My suggestion would be to learn basic Linux and get a server up. Then learn firewall on that server and then how to configure and use a vpn on it - as a client AND a server. Then move on to switching and finally basic routing. At that point you’ll have enough general knowledge to know what you want to do next.