I'd like to reverse proxy to another reverse proxy

[francislavoie]

See this article:

Using Caddy as a reverse proxy in a home network

If you want to run a service inside a Local Area Network (LAN) such as your home or office – and especially if you want to be able to access it from outside that network – Caddy can help you accomplish this quite easily. This guide will show you how. It assumes you’ve never done this before, but that you have some technical proficiency and are somewhat knowledgable about your own network. Do this at your own risk. There are several ways to make private services accessible from other n…

Essentially, Caddy will be the point of entry into your network, so you can just let it manage TLS.

Of course, keep in mind that this assumes your LAN is trusted, and that there’s no bad actors connected to the network (they could intercept/sniff/manipulate the traffic between Caddy and your app).