Our experience is running wildfly behind a combination of stunnel and haproxy. I believe the configuration is much the same for running behind apache. The key is that haproxy or apache must add X-Forwarded-For headers to each request.
In our setup we have theses requests come in on port 8081.
In haproxy add the line
to the defaults section.
In the undertow subsystem configuration add the line:
<http-listener name="stunnel" socket-binding="stunnel" secure="true" redirect-socket="https" proxy-address-forwarding="true" enable-http2="true"/>
and in the socket-binding section add
<socket-binding name="stunnel" port="8081"/>
Then build and deploy the selfreg module
At that point it seems to deploy correctly and we can log in.