Hello everybody!
I have installed OpenWRT on Mikrotik hAP ac3 that I've bought recently. Everything is ok, except WiFi.
Did not succeed with current release 25.05.5 as well as with current snapshot and some earlier versions of OpenWRT. Also tried installing some other firmware for ipq4019 from repo, all without success. The device does not have any problems with its original RouterOS.
I also have identical device that I've bought about a year before, and WiFi is ok with OpenWRT.
dmesg output:
[ 13.563050] ath10k_ahb a000000.wifi: qca4019 hw1.0 target 0x01000000 chip_id 0x003b00ff sub 0000:0000
[ 13.563125] ath10k_ahb a000000.wifi: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[ 13.575050] 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
[ 13.953998] ath10k_ahb a000000.wifi: failed to fetch board-2.bin or board.bin from ath10k/QCA4019/hw1.0
[ 13.954091] ath10k_ahb a000000.wifi: failed to fetch board file: -12
[ 13.962601] ath10k_ahb a000000.wifi: could not probe fw (-12)
[ 14.894495] ath10k_ahb a800000.wifi: qca4019 hw1.0 target 0x01000000 chip_id 0x003b00ff sub 0000:0000
[ 14.894575] ath10k_ahb a800000.wifi: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[ 14.906535] 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
[ 15.312071] ath10k_ahb a800000.wifi: failed to fetch board-2.bin or board.bin from ath10k/QCA4019/hw1.0
[ 15.312162] ath10k_ahb a800000.wifi: failed to fetch board file: -12
[ 15.320582] ath10k_ahb a800000.wifi: could not probe fw (-12)
Does your serial by any chance start with HF ?
Yes, its HFB0...
I'll try to build with this patch, thank you!
It worked! Thank you very much!!! You saved me 
But why this patch was not accepted for mainline OpenWRT yet?
No idea, did you use the updated patch ?
@robimarko, here's the confirmation you were looking for, in MikroTik HAP AC3 WiFi - #7 by robimarko.
I used one from pull request 13690.
the "wrong" one then, care to redo, using the 2nd one ?
Second patch, pull request 15774. Dear maintainers, please review the patch: it can not be applied to some makefiles due to kernel version mismatch! I had to edit it manually.
Compiled and flashed it. WiFi seems to work. Gonna test it more further.