Comment 49 for bug 1848921

I am using a Thinkpad E490 with the Intel 9260 wireless card, Kubuntu 19.10 and kernel 5.3.0-29-generic.

05:00.0 Network controller: Intel Corporation Wireless-AC 9260 (rev 29)

I have tried several iwlwifi module options (11n_disable=1, 11n_disable=8, power_save=0, bt_coex_active=0, lar_disable=1, swcrypto=0), older firmwares, as well as the dkms backport module. I have tested nearly all variations and the error did not disappear.

This is what I can summarize:

The error occurs after booting Windows (Fast Boot is disabled - which has no positive effect) and then booting Linux afterwards.
The error is quickly reproducible using speedtest.net (thanks @Hairong Zhu (hrzhu)) or transferring a larger file of any kind.

The ONLY solution to the problem in my case is:
Shutting the system down and removing the power adapter. Then boot Linux and the error is gone (no module options, current firmware iwlwifi-9260-th-b0-jf-b0-46.ucode, kernel 5.3.0-29-generic).

Never boot from Windows to Linux without powering down completely, then you should be fine until a fix is available.