The work was picked up and completed.

Rust:

https://github.com/sunrise-choir/ssb-legacy-msg/blob/master/...

https://github.com/sunrise-choir/ssb-publish/blob/master/src...

https://sunrise.social/

Go:

https://github.com/cryptoscope/ssb/blob/master/message/legac...

https://github.com/cryptoscope/ssb/blob/master/message/legac...

https://planetary.social

Spec:

https://spec.scuttlebutt.nz/feed/messages.html#json-encoding

https://spec.scuttlebutt.nz/feed/datamodel.html#signing-enco...