Yes, there’s a template you can add to your app.yml which will pass the client IP that Cloudflare forwards into Discourse. Add cloudflare.template.yml to the templates block as follows:
templates:
- "templates/cloudflare.template.yml"
And then rebuild.
I don’t think this is true at all, providing a rule is created to “disable performance” for the Discourse URL so that no extra optimisations or minification interferes with the payload and Brotli is disabled at a domain level there aren’t any real issues.
It does add unnecessary hops from client to server, which can delay requests by a small amount, but otherwise it works fine.