Could I just plug my old router into our modem without my roommate's Eero notifying him?

The eero isn’t inspecting packets. If it is I’d love to see the interface for it. All the advanced eero features are DNS based

OP wants to watch porn on their laptop / phone, so I guess you have to change it on those machines. You change it once and it’s done. Honestly this is no biggie. Why would you reset the network settings? But if you do, you’ll need another 5-10 minutes to put it back. Is that a big deal? I dunno.

If you plug in your own router now you’re double natting, not a particularly good solution either to be honest.

A VPN does more than just encrypting data packets. And secondly, this has nothing to do with packet sniffing.

I know what a VPN does. It’s a great solution when you don’t trust the Wi-Fi provider. But I don’t think the roommate has any capability of looking at the packet flow here. You know what else a VPN does? Changes the DNS provider.

Lmfao. What do you think a VPN does and a DNS service does? And do you think the roommate is running a packet sniffer? Is that what you got from OPs question? Even though that is absurdly wrong, why do you think DNS server change, of all things, will help with that?

I can confirm eero uses DNS-based tracking for analytics, but I can’t find an official statement. Changing your DNS and/or using a VPN should prevent site tracking analytics since it’s incredibly inefficient for home routers to filter based on IP addresses or packet sniffing.