Rank 5: Hypervisor
I have Cloudflare Access Tunnels in front of my Appwrite instance. When creating a CNAME in Cloudflare for my custom domain, if I don't enable Proxy, CF doesn't actually pass the traffic along at all. But if I do enable it, Appwrite won't verify the domain. I've been able to get around this by disabling Proxy for a couple of seconds whenever I want to add a domain, but this is not optimal.
I would expect Appwrite to actually just check if the domain I've entered points to Appwrite - try making a HTTP request to an expected endpoint or something.