Networking noob here. I want to prevent all incoming requests except through a specific port, and that traffic is forwarded to a specific device on the network. NAT seems to do that just fine, it’s almost like a kind of firewall by itself. What kind of threats are there that requires more than just NAT for security?
This is true and typically called “Next Generation Firewall” or “Intrusion Prevention System”.
However, these have three disadvantages:
These systems are quite common in enterprise scenarios, but AFAIK the exception in home labs and selfhosting environments.