These days Kestrel can be exposed to the outside world.

Kestrel is a cross-platform web server. Kestrel is often run in a reverse proxy configuration using IIS. In ASP.NET Core 2.0 or later, Kestrel can be run as a public-facing edge server exposed directly to the Internet.

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/?view=aspnetcore-7.0&tabs=windows#servers