Linux bridge uses EtherType 0x8100 by default. In some scenarios, an EtherType value of 0x88A8 is required.
IFLA_BR_VLAN_PROTOCOL Set the protocol used for VLAN filtering. The valid values are 0x8100(802.1Q) or 0x88A8(802.1AD). The default value is 0x8100(802.1Q).
You can change the value as follows:
echo 0x88a8 > /sys/class/net/br0/bridge/vlan_protocol