Just figured it out!
Adding this endpoint to my Startup.cs gives me access to everything I need:
endpoints.MapFallbackToPage("/{param?}", "/_Host");
For those that are 100% new, here is a more complete code snippet:
app.UseEndpoints(endpoints =>
{
endpoints.MapBlazorHub();
endpoints.MapFallbackToPage("/{param?}", "/_Host");
endpoints.MapFallbackToPage("/_Host");
});