Anyone with account to Ath11k bug report page wishing to file a bug?
At developers, I've just tried the official regular OpenWrt master build (Non NSS) with latest Ath11k firmware WLAN.HK.2.9.0.1-01862 and the issue is absolutely reproducible every time for my setup described in the first post.
I've even tried with reset to default but no success either.
I've tried the official regular OpenWrt master build (Non NSS) with Ath11k firmware WLAN.HK.2.9.0.1-01385 too. There is no issue with it keeping the same settings and packages installed.