How enable SSL for NextCloud13 Container on NAS?

Hello,

I installed NextCloud13 in a LXC Linux (Ubuntu 16.04) Container on a Qnap NAS.
The only problem it works without SSL at this moment.

Set the network settings in Qnap’s Container Station for the LXC container in NAT-mode.
Host: 1080
Container: 80

So NextCloud is accessible via:

http://192.168.0.201:1080 (LAN)
http://my-name.myqnapcloud.com:1080 (WAN)

Does anyone know how to setup SSL, so my NextCLoud Linux Container is accessible with https?
Or someone’s experience with this setup?

PS: asked also on Qnap’s forum (https://forum.qnap.com/viewtopic.php?f=354&t=142498) a few days ago, but at the moment without answer. Hope that someone can help me with this problem?

Regards,
Christophe