Comment 39 for bug 1848921

I've been having the same problem, the workaround I have is to use older firmware.

download:

https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/snapshot/linux-firmware-e58cbf78678fd872d0cf7ab858ba0030cd8695b0.tar.gz

and install the ./iwlwifi-9260-th-b0-jf-b0-34.ucode blob to /lib/firmware

I have also added an /etc/modprobe.d/wifi.conf with the following:
options iwlmvm power_scheme=1
options iwlwifi swcrypto=0 bt_coex_active=0 power_save=0 11n_disable=1

However I know that none of them except the 11n_disable option actually fixed the problem -- disabling the 11n setting MIGHT be a workaround as well, however I haven't tested with the broken firmware to know. [the reason is because other bug reports have confirmed the older firmware alone fixes the issue].