malformed HTTP response with docker private registry (v2) behind an nginx proxy
proxy_pass http://docker-registry.example.com:5000;
you are passing the request with plain HTTP (i.e. no https)
\x15\x03\x01\x00\x02\x02
And you are getting a SSL response back. So it looks like you must use https:// and not http:// to access port 5000. And you even know that you are using SSL:
The registry is running on port 5000, and is using an SSL key signed by a trusted CA...
Apart from that: please use the names reserved for examples like example.com and don't use domain names in your example which don't belong to you.