For starters, Reticulum can communicate over a Yggdrasil network natively, but no one has yet implemented a Yggdrasil link over Reticulum as far as I am aware.
A Yggdrasil link is an IP tunnel. Reticulum has its own network protocol instead of IP because IP would not work well over slow and low-bandwidth connections. I think tunneling IP through Reticulum would cause only headaches.
A few years back, I ran Yggdrasil (poorly) over LoRa using a then-available experimental Meshtastic IP tunnel. Reticulum supports text-only websites (in the NomadNet software), and I have tested how these load over LoRa links. Loading time on a single hop (lab conditions) isn't half bad, honestly.
My point in telling you this is that much of the mesh networking space is proof of concepts and poor executions, which often must happen first before elegant solutions to real problems can form.
My 2¢ on why Meshtastic is so popular (despite its many flaws) is because the original developer decided to implement a solution for a real use case.
