Visual Studio 2019 has a new entry under the Text Editor options named C#_LSP. I guess it has something to do with the Language Server Protocol, but I couldn't find what the entry is used for exactly.
Is there certain standard tooling that uses it? Or is it there for extensibility?
This is a bug. Internally some stuff is implemented with an LSP for Visual Studio Live Share, but a side-effect of that implementation was the C#_LSP entry appears. The entry doesn't do anything.
The Language Server Protocol (LSP) is a common protocol, used to provide language service features to various code editors. Using the protocol, developers can write a single language server to provide language service features like IntelliSense, error diagnostics, find all references, and so on, to various code editors that support the LSP. Traditionally, language services in Visual Studio can be added by using TextMate grammar files to provide basic functionalities such as syntax highlighting or by writing custom language services that use the full set of Visual Studio extensibility APIs to provide richer data. With Visual Studio support for LSP, there's a third option.
Source: https://learn.microsoft.com/en-us/visualstudio/extensibility/adding-an-lsp-extension?view=vs-2019
Based on this I assume that the C#_LSP option is for a case when you decide not to use build-in C# services and use LSP instead.
Personally I don't see any common use case for it, but I am sure there are people out there who like it that way.
