I have this device too and I think it's works. Not out of the box. Here my solution.
First I tried it with release 21.02.0 and with a self-compiled-snapshot. Both with the same result. So my description is for 21.02.0.
You need a ssh-access for it.
First I propose to delete the configuration and start with a fresh file:
rm -f /etc/config/wireless
wifi config
So the file /etc/config/wireless look like:
config wifi-device 'radio0'
option type 'mac80211'
option channel '36'
option hwmode '11a'
option path '1e140000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0'
option htmode 'VHT80'
option disabled '1'
config wifi-iface 'default_radio0'
option device 'radio0'
option network 'lan'
option mode 'ap'
option ssid 'OpenWrt'
option encryption 'none'
config wifi-device 'radio1'
option type 'mac80211'
option channel '36'
option hwmode '11a'
option path '1e140000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0+1'
option htmode 'VHT80'
option disabled '1'
config wifi-iface 'default_radio1'
option device 'radio1'
option network 'lan'
option mode 'ap'
option ssid 'OpenWrt'
option encryption 'none'
We have 2 interfaces with the same band (5.7 GHz), the same channel and the same SSID. And without Encryption.
My target: both bands (2.4 GHz and 5.7 GHz), diffferent SSID and Encryption.
I changed the wireless-file:
`config wifi-device 'radio0'
option type 'mac80211'
option path '1e140000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0'
option band '2G'
option htmode 'HT20'
option hwmode '11g'
option channel '3'
option cell_density '0'
option country 'DE'
config wifi-iface 'default_radio0'
option device 'radio0'
option network 'lan'
option mode 'ap'
option ssid 'guest-2'
option encryption 'psk2'
option key '123456789'
config wifi-device 'radio1'
option type 'mac80211'
option path '1e140000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0+1'
option band '5g'
option hwmode '11a'
option channel '140'
option country 'DE'
option htmode 'VHT80'
option cell_density '0'
config wifi-iface 'default_radio1'
option device 'radio1'
option network 'lan'
option mode 'ap'
option ssid 'guest-5'
option encryption 'psk2'
option key '123456789'
After reboot I checked the wireless-status in LuCI. Both bands were visible, only the first interface worked. So I restarted the second interface with LuCI and some times later, both interfaces worked (1 or 2 minutes later).
After reboot the same: only the first interface worked.
So I edit the file /etc/rc.local (or use LuCI: System / Startup / local Sttartup):
# Put your custom commands here that should be executed once
# the system init finished. By default this file does nothing.
sleep 60
/sbin/wifi
exit 0
So I'm very happy with my new device. Please change the country, SSID and your password