New installation self hosted on UBUNTU server 18.04 using custom port, but error

Hi, in my small office we have a couple of server/software on various VM, but only 1 dinamic IP.

We solve the dynamic IP issue using duckdns, which gives us 5 IP
myserver1-mydomain.duckdns.org
myserver2-mydomain.duckdns.org
and so on

My server/software have lets say the following LAN addresses
192.168.1.1 for server/software 1
192.168.1.2 for server/software 2

Now since almost all server/software requires port 443 for beeing securely accessible form abroad, we have a problem since I can forward port 443 only to one single internal address (for example to 192.168.1.1 only and not to another LAN address).

So I was thinking of using a different port, for example for a Jitsi server, the follwoing address to be accessible abroad

https://jitsi-server-mydomain.duckdns.org:20100
and then forward the following ports
port 20100 to port 443 at the address 192.168.1.2 (where I host VM with Ubuntu server on which I installed Jitsi server).
port 10000 UDP to 192.168.1.2
port 4443 TCP to 192.168.1.2

During installation I opened port 80 to 192.168.1.2, so the script
/usr/share/jitsi-meet/scripts/install-letsencrypt-cert.sh
came out without error

But now when I go to the address

https://jitsi-server-mydomain.duckdns.org:20100

it logs in, but then it disconnects, and tries to riconnect

Any hint?

I changed the file /etc/jitsi/videobridge/sip-communicator.properties as below

org.ice4j.ice.harvest.NAT_HARVESTER_LOCAL_ADDRESS=192.168.1.11
org.ice4j.ice.harvest.NAT_HARVESTER_PUBLIC_ADDRESS=myname.duckdns.org:20100
org.ice4j.ice.harvest.DISABLE_AWS_HARVESTER=true
# org.ice4j.ice.harvest.STUN_MAPPING_HARVESTER_ADDRESSES=meet-jit-si-turnrelay.jitsi.net:443

I tried also to change the below line taking out the port
org.ice4j.ice.harvest.NAT_HARVESTER_PUBLIC_ADDRESS=myname.duckdns.org

but results is same, I always get disconnected