Complete:
dpkg install ath10k-board-qca4019
Reboot.
root@OpenWrt:~# lspci -nn
root@OpenWrt:~# dmesg | grep \ ath
[ 12.835780] ath10k_ahb a000000.wifi: qca4019 hw1.0 target 0x01000000 chip_id 0x003b00ff sub 0000:0000
[ 12.835856] ath10k_ahb a000000.wifi: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[ 12.847847] ath10k_ahb a000000.wifi: firmware ver 10.4b-ct-4019-fW-13-5ae337bb1 api 5 features mfp,peer-flow-ctrl,txstatus-noack,wmi-10.x-CT,ratemask-CT,regdump-CT,txrate-CT,flush-all-CT,pingpong-CT,ch-regs-CT,nop-CT,set-special-CT,tx-rc-CT,cust-stats-CT,txrate2-CT,beacon-cb-CT,wmi-block-ack-CT,wmi-bcn-rc-CT crc32 6b2b5c5b
[ 12.876056] ath10k_ahb a000000.wifi: Loading BDF type 0
[ 13.070241] ath10k_ahb a000000.wifi: failed to fetch board data for bus=ahb,vendor=0000,device=0000,subsystem-vendor=0000,subsystem-device=0000,variant=MikroTik-hAP-ac from ath10k/QCA4019/hw1.0/board-2.bin
[ 13.254578] ath10k_ahb a000000.wifi: failed to fetch board-2.bin or board.bin from ath10k/QCA4019/hw1.0
[ 13.254651] ath10k_ahb a000000.wifi: failed to fetch board file: -12
[ 13.263058] ath10k_ahb a000000.wifi: could not probe fw (-12)
[ 14.099370] ath10k_ahb a800000.wifi: qca4019 hw1.0 target 0x01000000 chip_id 0x003b00ff sub 0000:0000
[ 14.099453] ath10k_ahb a800000.wifi: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[ 14.111434] ath10k_ahb a800000.wifi: firmware ver 10.4b-ct-4019-fW-13-5ae337bb1 api 5 features mfp,peer-flow-ctrl,txstatus-noack,wmi-10.x-CT,ratemask-CT,regdump-CT,txrate-CT,flush-all-CT,pingpong-CT,ch-regs-CT,nop-CT,set-special-CT,tx-rc-CT,cust-stats-CT,txrate2-CT,beacon-cb-CT,wmi-block-ack-CT,wmi-bcn-rc-CT crc32 6b2b5c5b
[ 14.139736] ath10k_ahb a800000.wifi: Loading BDF type 0
[ 14.150432] ath10k_ahb a800000.wifi: failed to fetch board data for bus=ahb,vendor=0000,device=0000,subsystem-vendor=0000,subsystem-device=0000,variant=MikroTik-hAP-ac from ath10k/QCA4019/hw1.0/board-2.bin
[ 14.340291] ath10k_ahb a800000.wifi: failed to fetch board-2.bin or board.bin from ath10k/QCA4019/hw1.0
[ 14.340380] ath10k_ahb a800000.wifi: failed to fetch board file: -12
[ 14.348854] ath10k_ahb a800000.wifi: could not probe fw (-12)