[Blazor] Settings applicationCulture in JSInitializer

[glatzert]

I'm currently trying to automatically set the WebAssembly language to the same what the server is using for that specific user.
To have it more or less automated in our environment, we're trying to implement it in a JSInitializer like so:

export const beforeWebAssemblyStart = (options, extensions) => {
    console.debug('Running beforeWebAssemblyStart', options);

    options.applicationCulture = document.documentElement.lang || "de-DE"
};

Despite that, it'll fallback to the first accept-language headers value.
Is what we're doing unsupported?

I know I can just move that code to Blazor.start(), but I would like to have in a central place, instead of every applications App.razor

[tossnet]

Have you tried it just like this? : add this into the .csproj ?

<PropertyGroup>
<BlazorWebAssemblyLoadAllGlobalizationData>true</BlazorWebAssemblyLoadAllGlobalizationData>
</PropertyGroup>

and this in program.cs :

CultureInfo.DefaultThreadCurrentCulture = CultureInfo.GetCultureInfo("de-DE");
CultureInfo.DefaultThreadCurrentUICulture = CultureInfo.GetCultureInfo("de-DE");

await builder.Build().RunAsync();

[glatzert]

My goal is to use the same language on the client as in the "prerendered" Variant of the page - e.g. rendered on the server and language selected via RequestLocalization. So getting the culture from host to client is the real problem here.
Also I want it to be as autmated as possible so ideally, I wouldn't need anything besides my own hosting packages, that wrap the application builders.

The solution is essentially here: https://learn.microsoft.com/en-us/aspnet/core/blazor/globalization-localization?view=aspnetcore-9.0#dynamically-set-the-client-side-culture-by-user-preference

But I wondered why I can easily set how blazor dependencies are loaded via the beforeWebAssemblyStart, but I cannot set the applicationCulture..