I have the same issue with talk.libreho.st. I have successfully installed in the app 10 Discourse instances on TLDs ranging from .org to .wiki and .network, but this one fails.
responds to port 80 with 301 redirect to port 443
has a valid SSL certificate
no error logged on the web server
Checked with:
curl -I -v http://talk.libreho.st/curl -I -v https://talk.libreho.st/
Tried both without and with the scheme.
Edit: I’m running version 1.2.1, will upgrade to 1.3.0 first…