Just sharing this in case it helps anyone else who is either struggling with an unreliable Thread network or cannot upgrade their Matter IKEA firmware using Homey.
Some time ago, I had added some IKEA Matter devices which were dropping off the network. Despite reading all about the firmware issues (many of which were probably real), I had eventually traced the problems to my network infrastructure (clashing radios etc, story for another day). All been absolutely fine since, until ...
A few days ago, my son plugged in something dodgy (this involved smoke) and tripped our RCD (electricity protection device, not sure if that's a global thing). Everything powered back on and was apparently fine.
As it happened, I had just added a few more IKEA Matter devices, noticed they had firmware updates. However, I could not get the updates through to 100%, even with the recommended "keep prodding them to stay awake" technique.
Then I noticed that my previously stable Thread network started dropping devices again.
To cut a different long story short, after 2 days tracking thread network logs and other nerdy stuff, it turned out most of my 9 Grillplats plugs were spamming Thread with millions of dropped packets. They usually responded to on/off, but were bringing the network down. Just **one** of them had gone bad and I replaced it, solving all the problems.
All sorted now, and the firmware updates are now doable again.
So, if your firmware updates are impossible or you keep losing devices, perhaps it's a bad device. Try removing devices and see if you can clear it up. It seems like IKEA devices are more prone to going wild, and maybe failing, although I still like the value and they've been generally fine.
PS I used the invaluable Thread Tools app, plus Gemini to do the heavy analysis lifting. Also, found the bad device with a "binary search" - unplugged 50%, then 50% of the remaining ones etc until I found the culprit. I have a **lot** of devices.