As Juerg's noted, the error message is indeed safely ignored, and there's a new firmware for the wifi chip upstream. I spent a bit of time on Friday trawling through the history in the upstream firwmare repos and came across a couple of intriguing commits.

Specifically, the commit [1] which updates the wifi firmware notes it is for certain variants of the Pi Zero 2W (there's an associated issue [2] which is an interesting read). The second fascinating commit [3] was, curiously, in the boot firmware. The interesting bit of that commit is "firmware: platform: over-voltage Zero 2 W by two pips". The associated bug [4] indicates that there is a suspicion (unconfirmed at the time of writing) that on some models of the Zero 2W the voltage calibration is marginal and this *may* result in unreliable wifi performance, so the firmware update bumped the voltage handling by default.

I've now built an experimental linux-firmware-raspi package with the bumped wifi and boot firmwares incorporated. It can be found with builds for kinetic and jammy in ppa:waveform/firmware [5]. I would be interested to hear if this firmware package improves your wifi. To test:

  $ sudo add-apt-repository ppa:waveform/firmware
  $ sudo apt install linux-firmware-raspi
  $ sudo reboot

To revert to the current jammy firmware (in case of issues):

  $ sudo add-apt-repository -r ppa:waveform/firmware
  $ sudo apt install linux-firmware-raspi=6-0ubuntu3
  $ sudo reboot

One other thing that may be worth trying is explicitly setting the wifi region (this can make a considerable difference to reliability in certain regions). Currently there's no "good" way of doing this since the crda package was removed upstream (the act of placing the region in /etc/default/crda no longer works). The wifi region can be set ephemerally with "sudo iw reg set" but the only method of persisting it (currently [6]) is to modify the kernel command line. Thankfully though, this isn't terribly difficult on a Pi.

Assuming "FR" is your region, the following would set the region in your current session, and persist it for future boots:

  $ sudo apt install iw
  $ sudo iw reg set FR
  $ sudo sed -i -e 's/$/ cfg80211.ieee80211_regdom=FR' /boot/firmware/cmdline.txt

If it's not too much trouble, I'd be interested to hear if either of these fixes improves things in isolation. In other words, assuming the wifi region is currently unset, I'd be interested to know if *just* updating the firmware fixes things and then if not, if fixing the wifi region improves things (and if so, perhaps roll back the firmware and see if it's still fixed?). This is simply because backporting firmwares is always a bit of a risky business and if wifi issues can be fixed by regulatory domain alone, that's a much safer alternative!

[1]: https://github.com/RPi-Distro/firmware-nonfree/commit/28bad1ec2ef72a33bf84d5c35d1eabc6951506ad

[2]: https://github.com/RPi-Distro/firmware-nonfree/issues/23

[3]: https://github.com/raspberrypi/firmware/commit/274d0c8ac0ec0850193618dce55c005832f918ea

[4]: https://github.com/raspberrypi/firmware/issues/1723

[5]: https://launchpad.net/~waveform/+archive/ubuntu/firmware

[6]: A facility to add the wifi regulatory domain has been committed to netplan, but not yet released -- https://bugs.launchpad.net/netplan/+bug/1951586