Do you mean the language servers or the actual extensions? Because, e.g., the IntelliJ extension doesn’t use a language server at all, and I think ocaml-lsp is used by several VS Code extensions (some of which, AFAIK, don’t plan to support the ReScript syntax ).
I mean the lowest denominator. For some it’s the language server and for some it’s the extension depending on the editor extension. I will add IntelliJ extension to the poll @hoichi. I cannot add more options now. For all the others it’s none of above then
Actually it uses neither merlin nor ocamllsp. It only defines a syntax and a bunch of helpful commands. Then on top of it you can enable either merlin or lsp-mode, both work. Only merlin is documented in the readme because when it was written there was no lsp server for ocaml. If someone feels like improving the readme I’d be happy to review a PR.