Ok, I've found a solution. (Took it from: https://forum.openwrt.org/t/tp-link-archer-c60-v2-19-07-0-rc2-ath79-snapshot-out-of-memory )
Archer C7 v2 / v5 - Connect via SSH and change firmware packages for the radio0 5 GHz interface:
- opkg remove ath10k-firmware-qca988x-ct kmod-ath10k-ct
- opkg update
- opkg install ath10k-firmware-qca988x kmod-ath10k
- rmmod ath10k_pci; sleep 1; modprobe ath10k_pci
- -OR- reboot
I'm able to run multiple AP SSID's and a mesh SSID with WPA3-SAE encryption simultaneously with the non-ct firmware packages.
/etc/config/wireless:
config wifi-device 'radio0'
option type 'mac80211'
option channel '36'
option hwmode '11a'
option path 'pci0000:00/0000:00:00.0'
option htmode 'VHT80'
option txpower '20'
option country 'DE'
option legacy_rates '0'
option noscan '1'
config wifi-device 'radio1'
option type 'mac80211'
option hwmode '11g'
option path 'platform/ahb/ahb:apb/18100000.wmac'
option channel '1'
option htmode 'HT40'
option country 'DE'
option legacy_rates '0'
option noscan '1'
option txpower '20'
....
config wifi-iface 'wifinet9'
option device 'radio0'
option mode 'ap'
option encryption 'none'
option ssid 'WLANHST-GAST'
option disassoc_low_ack '0'
option network 'VL134'
config wifi-iface 'wifinet10'
option network 'nwi_mesh0'
option mesh_rssi_threshold '0'
option key 'MYSECRETKEY'
option encryption 'sae'
option device 'radio0'
option mode 'mesh'
option mesh_fwding '0'
option mesh_id 'test_mesh_ssid'
This requires /etc/config/network to have the interface "nwi_mesh0".