The http: section in the config kills my UI and SSH

Installation Home Assistant OS
1

I’m trying to configure DuckDNS for remote access of hass.io. I followed the guide here.

As soon as I put the http: section into the configuration.yaml file and reboot, my UI becomes inaccessible and SSH connection no longer works. I can still see the SAMBA share, and there is a log file there with a bunch of errors looking like:

2019-08-13 23:43:20 ERROR (MainThread) [homeassistant.core] Error doing job: SSL handshake failed
Traceback (most recent call last):
  File "uvloop/sslproto.pyx", line 500, in uvloop.loop.SSLProtocol._on_handshake_complete
  File "uvloop/sslproto.pyx", line 484, in uvloop.loop.SSLProtocol._do_handshake
  File "/usr/local/lib/python3.7/ssl.py", line 774, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [SSL: HTTP_REQUEST] http request (_ssl.c:1076)`

I’m pretty new and any help would be appreciated.