csharp-ls
Roslyn-based LSP language server for C#
...However, it has been reported to work with projects using older versions of dotnet SDK, including .NET Core 3, .NET Framework 4.8 and possibly older ones too as it uses the standard Roslyn/MSBuild libs that Visual Studio & omnisharp does. csharp-ls implements the standard LSP protocol to interact with your editor. However there are some features that need a non-standard implementation and this is where editor-specific plugins can be helpful. Supports automatic installation, go-to-metatada (can view code from nuget/compiled dlls) and some additional features.