Can you post your apache proxy configuration?
Personally I haven’t seen one of them in a long time.
I think the Univention Appliance uses apache as a reverse proxy internally, so perhaps you can try to find that.
Also have you checked whether there is something in the log files, when logging in through the proxy?
Check all logs:
Browser (dev console → network tab [-> export as .har])
firstly I’d advise you to have a look at the Reverse Proxy documentation
Secondly, maybe it comes from the fact you don’t send the X-Forwarded-Proto header to your ownCloud, so ownCloud tries to force HTTPS.
Yes I spent many time on the documentation looking for useful tips. The documentation you are referring, is more a theory than a practical doc.Help me and may be we can use this case to make the documentation more practical. I saw quit few issues with “login Loop”.
The documentation said “you can set the following parameters inside the config/config.php.” ok can you give an example ? because the format of the config file an array ?