There are several tools that are very useful for intranet sites. One to remember is the DNN.ActiveDirectory authentication provider - a bit "old", but still doing it's job (more or less).
Creating a self-signed certificates is a bit of a challenge. For intranet applications with a lot of users it is annoying to get a "Not secure" message. And normally, you can't get Let's Encrypt certificates for web servers that can't be reached from the Internet.
The core DNN Search is a good tool - but what to do when PDF files and other documents should also be found, or to get the newest changes? psSiteSearch is a good solution.