None of the above answers worked for me, using vscode 1.95.3, C# extension v2.55.29, and dotnet 9.0.100.

the C# extension / vscode-csharp / ms-dotnettools.csharp no longer uses omnisharp by default, it uses roslin now. Also, if omnisharp finds a .editorconfig file it will ignore omnisharp.json. the C# Dev Kit extension (vscode-dotnettools) must be uninstalled, and vscode-csharp must be configured to enable omnisharp and ignore editorconfig.

  "dotnet.server.useOmnisharp": true,
  "omnisharp.useEditorFormattingSettings": false

then @thornebrandt 's omnipath.json should work.

source: What changed about the C# extension for VS Code's IntelliSense in the v2.0.320 release?