Internet anonymity without Tor

Nation-state-resistant internet anonymity is hard because the physical infrastructure can be inspected by someone with a monopoly on violence.

Fiber optic cables cannot hide sender/receiver identities as the attacker can wiretap the cables and then follow the physical path to identify which cable exactly carries a given message. Then they can break into the building that the cable enters.
- (also fiber optic connections usually requires KYC in most countries, but that's a legal limit not a physical one)
Radio signals cannot hide sender/receiver identities as the attacker can triangulate the signal based on signal strengths. Then they can break into the building that is transmitting the signal.
- (also encrypted radio is illegal in many countries, but that's a legal limit not a physical one)

When considering nation-state-resistant anonymity, getting the metadata alone is enough to count as an attack. Metadata includes sender/receiver irl identities, sender/receiver pseudonyms, message sizes and timestamps.

Tor relies on the sender passing each message to three other random users before it reaches the receiver, and hoping the three intermediaries don't all collude with the attacker.

What if the sender just sent the message to everyone instead?

Assume ofcourse, that each person is pgp encrypting their messages.
Assume also that they share public proofs (via youtube, twitter etc) that their keys are not compromised.
Assume that each user sends a single payload of X bytes to all users each day. This payload can include encrypted messages to specific users. If they have less than X bytes to send, they fill the remaining bytes with junk data.
Assume each user sends their X bytes at approximately the same time each day.
Only the actual receivers of the content can decrypt the message. It is junk to everyone else.
Assume 'gpg --hidden recipient' was used, so there's no way to tell which pubkey was used to encrypt a given message, from a given set of pubkeys.

Throughput

8 billion users, each user has 1 gbps unmetered fiber optic
- 1 gbps / 8B = 0.016 bytes/s = 1350 bytes/day
100 million users, each user has 1 gbps unmetered fiber optic
- 1 gbps / 100M = 105.4 KB/day
100 million users, each user has 10 gbps unmetered fiber optic
- 10 gbps / 100M = ~1.03 MB/day

Potential problems

Real-time messaging not possible. This is slow like courier.
Running servers from residential area requires effort. ISPs and OS developers can make this difficult. Renting a cloud server to download the messages does not work, as the cloud server owner knows which subset of these messages you downloaded to your local machine or display.