I'm curious to see what information I'm blasting out to the various services I depend on for internet (ISP, DNS, probably Cloudflare, etc.).
Are there any easy to setup, entirely self-hosted tools I can run on my home network that would allow me to snoop on my own traffic.
I want more than just DNS, so I'm not just looking for pihole and its ilk. I want to see things like SNI and any non-protected traffic that any of the devices on my network might be sending that I just don't know about.
Ideally, it would be something I could leave on without affecting my speed/latency, but something to turn on occasionally and spot check would be better than nothing.
My router runs VyOS, so I should have quite a bit of flexibility in what I do with my traffic, though I never have figured out if/how to deploy custom software to it…
Often you can mirror ports on routers and switches, this lets you send the same packets to a device as gets sent to your router. This will allow you to use something like wireguard to capture the packets and inspect them. Unfortunately for you, the vast majority of traffic is encrypted these days. So most of the time you can see how much data is being transmitted to Google, but not what data. Tools like Fiddler will help you on a specific machine, where it can decrypt it on the fly.