UPDATE 10/4 6:47 EDT
I have been going through all the comments. THANKS!!! I did not know about the techniques listed, so they are extremely helpful. Sorry for the slow update. As I mentioned below, I got behind with this yesterday so work cut into my evening.
I ran a port scan. The first syntax, -p, brought no joy. The nmap software itself suggested changing to -Pn. That brought an interesting response:
nmap -Pn 1-9999 <Local IP Addr>
Starting Nmap 7.93 ( https://nmap.org ) at 2024-10-04 11:44 BST Failed to resolve “1-9999”. Nmap scan report for <Local IP Address> Host is up (0.070s latency). All 1000 scanned ports on 192.168.0.46 are in ignored states. Not shown: 990 filtered tcp ports (no-response), 10 filtered tcp ports (host-unreach)
Nmap done: 1 IP address (1 host up) scanned in 6.03 seconds
Just to be absolutely sure, I turned off my work computer (the only windows box on my network) and reran the same syntax with the same results.
As I read this, there is definitely something on my network running windows that is not showing up on the DHCP.
If you can, power stuff off and check if that web page is still available. Start with any Windows machines. It could be a virtual machine running inside of something else though.
Edit: here’s how to disable that web server https://superuser.com/a/1377078 . I’d do that on any Windows machines as well.
I shut off my only windows machine and it is still there.
I’d go around unplugging anything that might be connected to the network, like game consoles, smart TV, etc. It’s unlikely, but maybe something has copied that same screen to throw you off.
It is probably going to come to this.