Сделай curl localhost:5000
root@gitlab:/# curl http://localhost:5000/v2 -I -L
HTTP/1.1 301 Moved Permanently
Content-Type: text/html; charset=utf-8
Docker-Distribution-Api-Version: registry/2.0
Location: /v2/
Date: Fri, 09 Jul 2021 19:33:59 GMT
HTTP/1.1 401 Unauthorized
Content-Type: application/json; charset=utf-8
Docker-Distribution-Api-Version: registry/2.0
Www-Authenticate: Bearer realm="
https://gitlab.example.com/jwt/auth",service="container_registry"
X-Content-Type-Options: nosniff
Date: Fri, 09 Jul 2021 19:33:59 GMT
Content-Length: 87