In my experience, this is a combination of weak radio hardware, immature firmware, and a generally less stable Thread implementation on Homey.
On the Homey side, I managed to make my Matter-over-Thread devices much more stable by tweaking my Wi-Fi access points quite extensively. I disabled beamforming and reduced transmit power, which seems to have helped. What makes me think the issue is at least partly on Homey’s side is that I never had these kinds of problems before when the same devices were running on my Apple Thread network. To me, that strongly suggests that Homey’s Thread radio is not as strong or as stable as it could be.
Unfortunately, I still have moments where some devices briefly become unavailable, although they usually come back after a short time.
On the IKEA side, I shared the devices with Apple Home through multi-admin only to update the firmware, then removed them again afterwards. I also installed some smart plugs that act as Thread routers, such as Eve Energy and Onvis S4, close to the affected devices. Since then, things have generally been working quite well, apart from these short dropouts. To me, that again points to limited radio performance.
The good thing is that Thread is a self-healing mesh, so devices should normally rejoin the network quickly. However, this is also where Homey does not seem to handle things particularly well. IKEA devices may not be the only cause, but they do seem to make the underlying weakness much more visible.
There are external Thread antennas on the market that many Home Assistant users rely on successfully. Homey already has USB-C, so come on guys — please give us support for external antennas.
