[octoberfranklin]

> Where can I read more about VPN providers tagging internet-bound traffic on port 53 with the customer IP address?

First, read this: https://en.m.wikipedia.org/wiki/EDNS_Client_Subnet

And this: https://tools.ietf.org/html/draft-hardie-privsec-metadata-in...

Then, start a VPN provider and wait for the NSL to arrive, like Mozilla did.

Not a coincidence that they suddenly started pushing DoH hard shortly after launching their own VPN. Before that it was just another protocol; after the VPN they suddenly were in a big huge hurry to put people on DoH by default whether the system resolver supported it or not.