this is the relay implementation:
https://github.com/HORNET-Storage/hornet-storage
this is the codebase that implements this frangible variant of merkle trees:
https://github.com/HORNET-Storage/scionic-merkletree
i don't know exactly how well it works, haven't tested it, and actually i'm kinda facepalming right now because i was actually almost working with him but he never offered to pay me, i did some stuff and had a share of a bounty dangled at me and all this led to bad blood between me and him
but now i'm looking at it... here's a Go relay codebase that IS NOT from fiatjaf or mattn...
gonna give it a good poke