We use the Blazor Server hosting model, which is inherently incapable of running offline. For our specific use case, this is actually more ideal than any notion of offline capability. In this model, any LINQ would be running on the server.

Now, you certainly can run LINQ client-side if you were on a Blazor WASM (or hypothetically, Desktop) application. This is kind of the entire point of the stack.

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).