What would cause Blazor components in an ASP.NET Core MVC app to stop working after upgrading from .NET 8 to .NET 10?

I've been trying to upgrade my Orchard Core modules to .NET 10 and have been having an issue with my Blazor module.

I'm getting an error

405 - Method Not Allowed

on a request to /_blazor/negotiate?negotiateVersion=1.

The code is on the 'upgrade-to-NET10' branch on my GitHub:

https://github.com/DrewBrasher/OrchardCoreModules/tree/upgrade-to-NET10/DrewBrasher.OrchardCore.Blazor

I've tried adding:

builder.Services.Configure<RouteOptions>(options =>{    options.SuppressCheckForUnhandledSecurityMetadata = true;});

or this:

builder.Services.AddCors(options =>{    options.AddDefaultPolicy(policy =>    {        policy.AllowAnyOrigin()              .AllowAnyMethod()              .AllowAnyHeader();    });});

but that didn't help.