Hello @raul.medina here i described the same problem - until now with solution 
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May be setting up the apache2 to listen on port 4443 instead of 443 could work, but i didn’t tried it.
But on the thread above there is also the port 9980 remarked to be open through the firewall may be some rerouting are additionally required (as you pointed out on your question).
I have no picture how the communication works between NC and Colabora and i did not find any 
- so if you find a solution, please give me a hint 
- many thanks.