Lets Encrypt can set up automatic forwarding to https for you, or you can leave it alone.
I strongly recommend that you ALWAYS use SSL. This security is also necessary in the internal network.
I also don’t know what you want to read in the traffic. To debug problems with a web application you use the web browser developer tools.
Apart from that:
In a web application that lives on links and linking, how is anything supposed to work with a mixture of https and http addresses?
You also get problems with Collabora Online, Rocket.Chat, Guacamole or whatever you want to integrate in the future.
Please ALWAYS use https. You are doing yourself (and us) a big favour!