Oh I can tell what it was, I still use the most up-to-date-from-git version of the firmware from [1]. The testing back then wasn't successful, but I'm reluctant to go back to the base version as I'm afraid the error strikes me at some odd point when I really need wireless.
If anyone else is affected and could try if the PPA fixes it for him as well that might be helpful. [1]: https://launchpad.net/~paelzer/+archive/ubuntu/bug-1804841-iwlwifi- linux-firmware -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-firmware in Ubuntu. https://bugs.launchpad.net/bugs/1804841 Title: iwlwifi Microcode SW error detected. Restarting 0x2000000. Status in linux package in Ubuntu: Incomplete Status in linux-firmware package in Ubuntu: Incomplete Bug description: This seems to be a return of an existing bug, in newer hardware and microcode versions. Wireless card: Intel Corporation Wireless 8265 / 8275 [8086:24fd] (rev 78) Firmware version: 34.0.1 Description: Ubuntu 18.04.1 LTS Frequent errors as soon as I connect to wifi: Microcode SW error detected. Restarting 0x2000000. Expected to happen: Great and stable wifi like a couple of weeks ago What happens: very slow, intermittent internet access, lots of ping loss Found a suggestion of a workaround: adding these lines to /etc/NetworkManager/NetworkManager.conf [device] wifi.scan-rand-mac-address=no These lines were already there, not added by me. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: linux-firmware 1.173.2 [modified: lib/firmware/iwlwifi-8265-36.ucode] ProcVersionSignature: Ubuntu 4.15.0-39.42-generic 4.15.18 Uname: Linux 4.15.0-39-generic x86_64 NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair ApportVersion: 2.20.9-0ubuntu7.5 Architecture: amd64 Date: Fri Nov 23 15:23:54 2018 Dependencies: InstallationDate: Installed on 2018-09-03 (81 days ago) InstallationMedia: Kubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725) PackageArchitecture: all SourcePackage: linux-firmware UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1804841/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
