I asked on Reddit if there is anyone already developing a Ruby mode using tree-sitter.  They suggested ask here.  It seems volunteers were being solicited recently.

I don’t want to officially volunteer but if no one is working on one, I’ll start pecking at it.  I’m not confident enough to volunteer.  At least not until I’ve wadded deeper into it.

I’ve found https://tree-sitter.github.io/tree-sitter/ and a few other resources such as the start-guide in admin/notes/tree-sitter.  If there are any other helpful references, please let me know.  I plan on using typescript-ts-mode as a guide.

Thank you,
Perry