WiFi randomly (or under load) disconnects on Ubuntu 18.04 with Qualcomm Atheros QCA6174
I had the same issue, I solved it, at least it seems it works so far, by applying this workaround based on this solution.
Here the workaround:
Replace the folder
/lib/firmware/ath10k/QCA6174/hw3.0with the corresponding from https://github.com/kvalo/ath10k-firmware/tree/master/QCA6174/hw3.0Rename
firmware-4.bin_WLAN.RM.2.0-00180-QCARMSWPZ-1tofirmware-6.binRestart Ubuntu
Hope it helps.