I gave Sorbet a red hot go on a decently-sized codebase maybe a year ago. I stopped writing Ruby not long after coming to the conclusion that Sorbet is a dead end. I never seriously considered RBS; the idea of maintaining C-style header files always struck me a kind of nuts from a DRY perspective, and very antithetical to the elegance of Ruby.

I ended up rewriting my Ruby codebase in Elixir (with thanks to some kind pointers here on HN). Elixir has perfectly satisfactory gradual typing via Erlang's dialyzer, which will happily power an LSP right now, and work is underway on a handmade gradual set-theoretic type system. It's a direction of travel I feel more confident in than Ruby's.