Conceptually: you probably want to (transparently) pass VLAN 1511 (IPTV) to interface connected to TV box. Which means you will have to add ether1 to bridge (already spanning the rest of ether interfaces) and configure VLANs. There’s a good tutorial about configuring VLANs on ROS.
But conceptually: you need 3 VLANs:
VID 1354 tagged on ether1 and bridge interface. You also need vlan interface configured off bridge interface which will then be used by pppoe-client.
pppoe-client interface will be your logical WAN interface, so when added to WAN interface list the default firewall will allow you to use internet.
VID 1511 tagged on ether1 and any port connecting TV box (e.g. ether2)
arbitrary VID (e.g. 666, can be anything between 2 and 4094 except 1354 and 1511) tagged on bridge and untagged on LAN ports (e.g. ether3 and ether4, probably wlan1, perhaps ether2 as well depending on functionality of TV box). You also need vlan interface configured off bridge interface which will then be used for LAN access to router (e.g. it’ll host DHCP server for LAN, it’ll have router’s LAN address, … anything what default config puts on bridge).
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