How to see traffic usage on Dumb AP with DSA?

I have Xiaomi Router 4A Gigabit configured with 21.02.1 as a Dumb AP (wan port is attached to br-lan)
And I want to monitor traffic usage (e.g. wireless and cable).
With wlan0 and wlan1 no issues, I can see this as expected with ifconfig -a.

But as for cable traffic, looks like it does not count to any interface.
For example, I have a RaspberryPi connected with a cable to this Dumb AP, and the traffic used by it does not reflect anywhere. I suppose this is happening due to DSA, because on Archer C7 all the traffic is being reflected in some interface stats.
Also, when I open Status - Realtime Graphs in LuCI, I can't see this traffic flow on any graph.

I used eth0 to monitor the traffic, but this is a CPU interface. Thus, it only counts the traffic going through the CPU. Obviously, only wireless traffic goes through there and LAN traffic is just forwarded as is over the switch.

My ifconfig -a output:

br-lan    Link encap:Ethernet  HWaddr ********  
          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::5e02:14ff:fe06:c25e/64 Scope:Link
          inet6 addr: fd4b:7340:46a9::1/60 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1909595 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1523133 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:155567983 (148.3 MiB)  TX bytes:141061594 (134.5 MiB)

eth0      Link encap:Ethernet  HWaddr ********  
          inet6 addr: fe80::5e02:14ff:fe06:c25e/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1504  Metric:1
          RX packets:12338031 errors:3 dropped:0 overruns:0 frame:0
          TX packets:45948042 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:14784291450 (13.7 GiB)  TX bytes:35977940037 (33.5 GiB)
          Interrupt:21 

lan1      Link encap:Ethernet  HWaddr ******** 
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7373298 errors:0 dropped:68 overruns:0 frame:0
          TX packets:17478688 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:9313178251 (8.6 GiB)  TX bytes:12311958673 (11.4 GiB)

lan2      Link encap:Ethernet  HWaddr ******** 
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1335673 errors:0 dropped:0 overruns:0 frame:0
          TX packets:27002139 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:434382033 (414.2 MiB)  TX bytes:23152475834 (21.5 GiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:146 errors:0 dropped:0 overruns:0 frame:0
          TX packets:146 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:12812 (12.5 KiB)  TX bytes:12812 (12.5 KiB)

wan       Link encap:Ethernet  HWaddr ********  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3629060 errors:0 dropped:42 overruns:0 frame:0
          TX packets:1464203 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:4814646608 (4.4 GiB)  TX bytes:145275724 (138.5 MiB)

wlan0     Link encap:Ethernet  HWaddr ********  
          inet6 addr: fe80::5e02:14ff:fe06:c260/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:43701969 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9933329 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:34824147514 (32.4 GiB)  TX bytes:14003284806 (13.0 GiB)

wlan1     Link encap:Ethernet  HWaddr ********  
          inet6 addr: fe80::5e02:14ff:fe06:c261/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:596720 errors:0 dropped:0 overruns:0 frame:0
          TX packets:730715 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:621498666 (592.7 MiB)  TX bytes:884254349 (843.2 MiB)

Is there any way to see cable traffic usage in this case?
Also, what means the numbers for lan1, lan2, wan interfaces if they do not reflect the actual traffic flow over these ports?