One other suggestion worth trying.
There is a good guide for qca wifi settings here. This is for ddwrt, so not everything in this guide is applicable to openwrt. However, check if the DTIM interval is
1 and the Beacon interval is
200 on both the 2.4GHz and 5GHz radios. If you don't have these values, try them as apparently it may help for some devices (like apple).
From the openwrt luci www GUI, both the DTIM and Beacon interval's can be found for each SSID via the "Network" menu, "Wireless" menu item. For each SSID under the "Wireless Overview" heading, chose "Edit".
"Beacon Interval" is found under the "Device Configuration" in the "Advanced Settings" tab.
"DTIM Interval" is found under "Interface Configuration" in the "Advanced Settings" tab.
Save after changing each value and don't forget to apply the saved changes. For good measure, you might want to disconnect/reconnect the problematic devices.
Don't go overboard with changing some of the settings from this guide (i.e. prim numbers for beacon interval or RTS/CTS settings until you've had a few days to evaluate any changes you've tried.
I rarely see these messages i.e. days between events with a wifi netowork up 24/7 (using ath10k-ct driver/htt firmware on a qca9980 wifi chipset).
On wifi, I've got 2 windows clients, 2 osx clients, 1 chrombook, 2 unbuntu clients, 1-2 android clients and at least 5 ios clients (at least part of the day all of them are on together).
Given the mix of complaints above as well as other ath10k users not experiencing any real issues, there are likely several causes for these messages, most are probably client or "location" related (think wifi interference) and, i suspect, none of them related to the ath10k driver or firmware.