Yes, but tagged VLANs need to be defined on the WAN port. The LAN port is not capable of handling tagged VLANs due to limitations in the DSA implementation.
example of my config
/etc/config/network
(snip)
config device
option type '8021q'
option ifname 'wan'
option vid '20'
option name 'wan.20'
config device
option type 'bridge'
option name 'br-wan-20'
list ports 'wan.20'
config interface 'wan_20'
option proto 'dhcp'
option device 'br-wan-20'
/etc/config/wireless
(snip)
config wifi-device 'radio1'
option type 'mac80211'
option path 'platform/soc/c000000.wifi'
option channel 'auto'
option channels '60 100 144'
option band '5g'
option cell_density '0'
option country 'US'
option htmode 'HE80'
option txpower '23'
option disabled '0'
config wifi-iface 'wifinet5'
option device 'radio1'
option mode 'ap'
option ssid 'VAP20ax'
option encryption 'psk2+ccmp'
option ifname 'r1_ax.20'
option network 'wan_20'
option key 'mykey1234'
bridge
root@AX3600:~# brctl show
(snip)
bridge name bridge id STP enabled interfaces
br-wan-20 7fff.88c397180e52 no wan.20
r1_ax.20
(snip)
...