https://trash-guides.info/Prowlarr/prowlarr-setup-proxy/ is useful when setting up the proxy in prowlarr for your indexers

Also we say don't put the arr's behind a VPN because cloudflare likes to just ban IP's at times which will result in the arr's not being abloe to access the arr metadata layers

just an fyi, DO NOT put your arr's behind a VPN it will cause issues https://wiki.servarr.com/radarr/faq#vpns-jackett-and-the-arrs