for the impatient, skip to the how-to
This article explains how to get a TLS Certificate for your LAN so you can use https:// and not have to ignore these “⚠️ Your connection is not secure” errors:
The reason that the browser throws this error is that TLS (and SSL before it) were designed to perform two functions:
Authenticate the website to the user (prove it is really that site, and not a MITM) and Secure the contents of the data that flows between the user and the website When you ignore this https error you are forgoing function #1, authentication, but you still get #2.