LINQ is built into the core .NET runtime (and the syntax into C#) and available everywhere (I think LINQ was introduced with .NET 4 and C# 3.0 some >10 years ag

LINQ is built into the core .NET runtime (and the syntax into C#) and available everywhere (I think LINQ was introduced with .NET 4 and C# 3.0 some >10 years ago). So doesn't matter if client/server or blazor. But you need some kind of LINQ-to-your-datasource adapter (i.e. to Sqlite, MongoDB etc.) which might have different availability depending on your environment (i.e. a Sqlite adapter would clearly somehow depend on a native sqlite client - but AFAIK is available in Blazor through WebAssembly).