It is this issue: https://dev.openwrt.org/ticket/21929
Do you have any USB3 port? Plugging the Wifi adapter in it may solve your problem. Otherwise, try a newer version of the firmware for its chipset by downloading the deb package on https://packages.debian.org/buster/all/firmware-ath9k-htc/download and installing it (with 'sudo dpkg -i' or double-clicking on the deb file after installing GDebi).
