Program.cs

using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Builder;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System.Reflection;

var builder = FunctionsApplication.CreateBuilder(args);

builder.ConfigureFunctionsWebApplication();

// Load log levels and categories from appsettings.json. Based on: https://github.com/Azure/azure-functions-dotnet-worker/issues/2531
builder.Configuration.AddConfiguration(
    new ConfigurationBuilder()
        .SetBasePath(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)!) // Required on Linux
        .AddJsonFile("appsettings.json") // First read configuration file
        .AddEnvironmentVariables() // Then override using app settings
        .Build()
        .GetSection("Logging")
    );

builder.Services
    .AddApplicationInsightsTelemetryWorkerService()
    .ConfigureFunctionsApplicationInsights()
    .Configure<LoggerFilterOptions>(options =>
    {
        // The Application Insights SDK adds a default logging filter that instructs ILogger to capture only Warning and more severe logs.
        // Application Insights requires an explicit override. Log levels can also be configured using appsettings.json.
        // For more information, see https://learn.microsoft.com/en-us/azure/azure-functions/dotnet-isolated-process-guide?tabs=hostbuilder%2Cwindows#managing-log-levels
        var toRemove = options.Rules.FirstOrDefault(rule => rule.ProviderName
            == "Microsoft.Extensions.Logging.ApplicationInsights.ApplicationInsightsLoggerProvider");

        if (toRemove is not null)
        {
            options.Rules.Remove(toRemove);
        }
    });

builder.Build().Run();