Guest WiFi with VLAN not bridging WAN port on the ap

I've a GL-iNet MT-6000 (r26746-832e2f6dd0 24.158.03388~a6f8361) as a router and I'd like to use a R7800 (r26620-6b03050192 24.158.03388~a6f8361) as a "dumb ap" with VLAN.

The dumb accesspoint has just 2 interfaces.

I got the LAN dumb ap working.
I'd like to get the guest ap on the wan port.

The lan5 in the MT-6000 has been removed from the br-lan bridge and I have created a bridge just for the lan5.
Then I created an interface with that bridge configured as static IP (10.66.6.253), DHCP server, different IP range from LAN.

I've created a WiFiGUEST firewall zone and I have a rule that let the WiFiGUEST zone access ports 67, 68, 53 on the device.

On the R7800 I'm trying to use the wan VLAN.

I've created a bridge that contains the wan interface.
and
/sys/class/net/wan/uevent:DEVTYPE=dsa
(up to my understanding wan is a vlan)

With that bridge I created an interface set as DHCP client.

I've the wifi interfaces assigned to the WiFiGUEST network.

This bridge interface doesn't get an IP.

I can see it is requesting one on the wan

tcpdump -i wan
21:04:30.856530 IP 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from b0:b9:8a:73:58:fd (oui Unknown), length 300

but not on the lan bridge. And that's what I'd expect.

Port lan5 and wan port are connected directly with a cable.

I can see wifi client successfully authenticating on the wifi "interfaces".

Nevertheless I can't see the dhcp requests arriving on lan5 of the router.

What am I missing?

thanks

OK... before I start to change the cfg...

I've read some posts, see some videos etc...

And I noticed they put all "ports" in the same bridge and then tag them etc...

Now there are devices with just one single ethernet connected to a switch.
And that makes perfect sense.

But many devices seems to have 2 ethernet, one connected to the "wan" port and the other to the lan switch.

This seems to be the case of the MT-6000 and the R78000

On MT-6000 I have eth0, eth1, lan[1-5]
/sys/class/net/eth0 has
upper_lan[1-5] as symlink...
/sys/class/net/eth1 doesn't and doesn't have a dsa subdir

On R78000 I have eth0, eth1, lan[1-4], wan
/sys/class/net/eth0 has
upper_wan as symlink
/sys/class/net/eth1 has
upper_lan[1-4] as symlink...

On the router side... I don't even have to put the eth1/wan on the megabridge.

But what are the implications of putting both eth0 and eth1 on the same bridge?

I can actually have lan traffic on the "switch" side of the router linked to eth0 and keep on using the rest of the "switch" port as a switch since my setup actually provide at least 2 cables between my ap and the router and I'd avoid to lock me out by mistake playing with vlans on the lan side.

How can I set up the router and the ap in a way that eg.
guest traffic will pass trough a cable from router-lan5 -> ap-wan
and I can use the rest of the ap switch ports as "switch"?

Does it make sense? It seems so even considering that I guess there could be some extra overhead and that ports may have different speeds (1G vs 2.5G).

thanks