I may be reading too much into this but it sounds like you’re searching for templates to stimulate ideas similar to how there are examples for smaller puzzle type problems.

I think most sizable stuff is proprietary. I implemented an lsp in an open source K which uses json/rpc. But the open source K is probably best considered a hobby project.

https://github.com/gitonthescene/ngnk-lsp/blob/kpath/k/lsp.k

You might consider joining one of the APL forums if you haven’t already.