Reticulum uses absolutely no blockchain. It uses a fairly novel routing strategy with something called announces.

Read this page to learn more about it: https://reticulum.network/manual/understanding.html

TL;DR it only flood routes packets that tell the network the location of a node; each node stores the “next hop” to get to every other node on the network. Everything else is routed along a single path determined by those “next hops.”