Just to share some experience: 100% privacy on these kind of networks is more a sympton of talking to software engineers than the radio reality observed on mesh networks.
Very often what comes as top priority is communication itself, which means radio-amateur radio frequencies where encryption is only available for signing messages but not the content.
Reticulum can be 100% private as it can choose to send packets in plain text. Can also broadcast messages without a specific target receiver, these are features that are necessary for radio transmission on amateur frequencies.
On LoRa: attention that default reticulum is still "too talkative". Meaning that in some LoRa frequencies there is a legal limit to how many messages (transmission time) your device can send per hour and even the automated announcements (to say "Hello, I'm here") quickly waste that available space.
On Internet: reticulum is great. I'm seeing about 700 connected devices across different hubs.
People often compare reticulum to Meshcore or Meshtastic but they often neglect one important aspect: those are exclusive LoRa implementations. Reticulum is the same protocol (language) no matter the network underneath. This means that you can connect a phone via BLE to a LoRa link which on the other side is connected on the Internet and then flies down to another BLE somewhere. This is not common to find on reticulum but possible.
There is a lot of good work on the topic. Maybe it will surface here on HN soon when more stable. In October there is an yearly event in Coimbra, Portugal where these topics are presented and tested in deep.
So what Matter is to Thread, Reticulum is to LoRa?
Yeah, I got the impression that Reticulum's main claim is that it replaces the IP stack with a future-proof, encrypted protocol for routing regardless of the underlying network medium. Which is not an insigificant claim to test, but boy would it be fantastic.
Would say your understanding is correct. It uses something similar to a "gossip" protocol where the public keys of other users are advertised.
So it gets ride of IP addresses and can jump boundaries between different network types. I'm using it for BLE to BLE communication, I've seen videos of people using it for USB to USB communication. There aren't many limitations as long as data can flow.