Help needed with Queue

Hello all,

So I have a kind of a complex setup and I need help with QoS or Queues.

I have an Rb4011 in my home country on which I am hosting a Wireguard server and an L2TP server which is bridged to an ETH port receiving an IPTV multicast traffic.

In the current country I am in, I have an Rb5009 on which I am tunneling back to the Rb4011 and using the Wireguard tunnel for my home LAN while I am using the L2TP tunnel bridging it to 1 ETH port where I have connected my STB which receives the IPTV multicast traffic from the Rb4011.

Now with the queues, I am looking to do the following. Set my IPTV STB to have Priority 1 and the LAN traffic which is through the Wireguard to be Priority 2 and then maybe further separate the traffic in the home LAN for better QoS.

I used the article here to set up the packet marking and the queue trees:
http://forum.mikrotik.com/t/using-routeros-to-qos-your-network-2020-edition/66683/1

The problem I have is how do I set up my IPTV STB which is on a different bridge with the L2TP tunnel to have first priority? Do I mark its traffic by the in-interface since it’s on one ETH port?

Thanks in advance!

Anyone?