This is xkcd’s (yes the comic guy) ‘What If’, the whole point of the video series is to answer what would happen if what happens didn’t happen.

The short trims it out, but “Everyone would die” is mentioned in the first 10 seconds of the full video: https://youtu.be/gp5G1QG6cXc

The browser extension also lets you scan the page for QR codes for the TOTP key.

And I feel like it’s not a good idea to have a modem directly attached to the pc directly unless you’re using it as a router?

Yeah I feel like this is the issue. The modem/router would be firewalling between the networks hiding the PC behind it.

Also from the description, does OP have a router at all? Is their ISP somehow just allocating public IPs to everything? Do your IPs start with 192.168 or something else?

Someone has also just done 100 modems over a T3 line using Cisco gear: https://youtu.be/rOdGK6GVIVU

https://archive.md/mVUfw