How to setup Unraid HA docker container to use mDNS (mediaplayers)

I do run HA as a docker container under Unraid.
That works fine.
Normally the HA docker is running as Host.
I like to change that to a custom network.
I did add port 8123 to the container and it is running fine.
Except the use of the mediaplayers. I use some google home minis for TTS.
So it would be nice to be able to use that again.
I did read some where that I need to expose mDNS at port 5353 UTP.
I do not know what that means and how to do.
If I try to add that port to the HA container, HA is not starting giving error that 5353 is already occupied.
I did search Google without any luck
So can somebody help me to use the mediaplayesr again at a custom HA network?
Thanks