wifi did work on the Mon Feb. 24 snapshot via imagebuilder (no other change).
A likely clue from dmesg:
[ 44.628614] ath10k_pci 0001:01:00.0: mac-vif-chan had error in htt_rx_h_vdev_channel, peer-id: 0 vdev-id: 0 peer-addr: XX:XX:XX:XX:XX:XX
I'm a bit preoccupied atm, but can respond (slowly) for requests for more info. Not sure yet where this question should go (@greearb or someone else...).
I'm successfully using r12315-e8fae62f64 from the 25th on my nbg6817/ QCA9984 (that commit is after the two ath10k-ct patches, but before the wifi reload ones).
ath10k_pci 0001:01:00.0: NOTE: Firmware DBGLOG output disabled in debug_mask: 0x10000000
ath10k_pci 0000:01:00.0: unsupported HTC service id: 1536
ath10k_pci 0000:01:00.0: 10.4 wmi init: vdevs: 16 peers: 48 tid: 96
ath10k_pci 0000:01:00.0: msdu-desc: 2500 skid: 32
ath10k_pci 0000:01:00.0: wmi print 'P 48/48 V 16 K 144 PH 176 T 186 msdu-desc: 2500 sw-crypt: 0 ct-sta: 0'
ath10k_pci 0000:01:00.0: wmi print 'free: 81800 iram: 13300 sram: 14440'
ath10k_pci 0000:01:00.0: Firmware lacks feature flag indicating a retry limit of > 2 is OK, requested limit: 4
I would suggest to build from source and try the relevant commit states individually:
f2fc7a62c012c6fc58a87b87cf123463c684a685 right before all these changes
930fc09803f1e75958d573bc55452b8ea61137be just after the two ath10k-ct changes
current HEAD (a1dd7732729a7b54890095187cd1766a773051d1 or later), including the wifi reload changes.
Edit: this is with ath10k-firmware-qca9984-ct-htt - 2019-10-03-d622d160-1
If it is just a warning about a bad reported rate, it should not be a real problem and you can ignore it. I have higher priority problems to work on first but will get to that eventually.