@dc42 I'm using a Duet 2 WiFi with firmware & DWC version 3.4.5. No expansion boards or RPI. To expand on my setup a bit, I'm running an ubuntu headless server with docker containers for traefik 2.10.1 and authelia. I'm then exposing via cloudflare tunnel (cloudflared) to avoid having to forward a port from my router. It's possible headers are being added at multiple stages through this chain, I was focusing on authelia because that was the straw that broke the camel's back so to speak.
As mentioned, removing authelia's four default authResponseHeaders (taken from here) reduced the number of headers such that DWC now loads in chrome with authelia in place, though I don't understand the system well enough to know if that is secure or if it causes any other problems.