Want to create a Caddyfile for Caddy2 that references a nextcloud reverse proxy on separate computer

[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…

Once you’re in your own network, there’s no reason to proxy over HTTPS, unless you have reason to believe something could intercept requests between Caddy and your upstream, maliciously.