I am running Hassio with Caddy + Cloudflare to access remotely securely on a raspberry PI and the same PI I have OMV 6, Portainer, Jellyfin, NextCloud and Duplicati.
My domain name is already working with nextcloud and jellyfin but I am unable to setup it up for Hassio as I am getting 400: Bad Request
Topic is old but one of top results when searching for this problem.
The only trusted_proxies that worked for me was ::1 (which is essentially the IPV6 equivalent of 127.0.0.1). Also I put it in a bulleted list (not sure that matters). Like so:
I got that address from looking at my logs (Settings → System → Logs).
Prior to that I had also tried 127.0.0.1 as well as the local IPV4 address of the machine but neither of those worked for me. Which is weird, because I don’t use IPV6 at all. But apparently that’s what Caddy uses when proxying to localhost? [0]
HTH
[0] Just speculating, as I just started playing with Caddy this evening.