I spent a long time trying to connect HAOS to my SMLIght SLZB-06M as my Open Thread Border Router using Ethernet not USB. I searched forums watched youtube videos and got nowhere. I decided to ask Claude AI to help me. And it worked! I asked Claude to summarise our successful 2 hour session and here it is. You will of course have to subsitute your own IP addresses. I think the key was finding and populating the correct value for the “Backbone Network Interface” value in the Configuration of the HA Open Thread Border Router App. When you add new devices use the HA Companion App on your phone.
Here’s Claude’s summary:
Solving OTBR + SLZB-06M Thread over Ethernet on HAOS x86/Laptop — Full Troubleshooting Guide
Setup:
- Home Assistant OS 17.1 (generic-x86-64) on a laptop
- SMLIGHT SLZB-06M flashed with Thread firmware
- SLZB-06M connected via Ethernet/PoE (not USB)
- OpenThread Border Router (OTBR) add-on v2.16.5
- IKEA KLIPPBOK Matter over Thread device
- FRITZBox 7590 router
- Android phone with HA Companion app
Problem 1 — OTBR crashing with /dev/ttyS1 error
The OTBR add-on crashed immediately on every start with:
termios.error: (5, 'Input/output error')
referencing /dev/ttyS1 (the laptop’s built-in motherboard serial port).
Red herring warning: This looks like a USB hardware error but it isn’t. The real cause was the backbone network interface field (enp3s0) not being set in the OTBR configuration. On HAOS with a dark theme this field was invisible/hidden in the UI.
Fix:
- Uninstall OTBR and select delete data when prompted
- Restart HAOS before reinstalling
- Reinstall OTBR from the Apps Store
- In configuration set:
- Network Device:
<SLZB-06M-IP>:6638(e.g.192.168.1.116:6638) - Backbone Network Interface: your LAN interface name (see below)
- Auto flash firmware: off
- Hardware flow control: off
- Network Device:
Note for x86/laptop users: Ignore any OTBR documentation references to plugging in a USB device — this is not needed or relevant for Ethernet mode.
Finding your backbone network interface name
This is device specific and will vary per machine. In the HAOS terminal run:
bash
ip addr | grep 192.168
The interface name shown next to your local IP address is what you need — common examples are enp3s0, enp2s0, eno1, eth0. Do not just copy someone else’s interface name.
If you have both wired and WiFi showing (e.g. enp3s0 and wlo1) always use the wired Ethernet interface for OTBR — WiFi can silently drop the IPv6 multicast traffic that Thread relies on.
Problem 2 — Companion app saying “This device requires a Thread border router”
Even with OTBR running perfectly and the Thread integration showing the border router with credentials, the HA Companion app on Android kept saying a Thread border router was required during Matter commissioning.
Fix — sync Thread credentials to your phone:
In the HA Companion app go to: Settings → Companion app → Troubleshooting → Sync Thread credentials
This pushes the Thread network credentials from HAOS to your phone. Without this step the phone doesn’t know about your border router during commissioning regardless of whether OTBR is running correctly. This step is easy to miss and not prominently documented.
After syncing, try commissioning again — it should work.
IKEA KLIPPBOK specific tips:
- Hold the reset button for 10 seconds until LED flashes rapidly before pairing
- Keep the device within 1-2 metres of the SLZB-06M during pairing
- Ensure IKEA device firmware is up to date before commissioning
- Multiple attempts may be needed — this is a known IKEA firmware issue
Other notes:
- The SLZB-MRW10 (Zigbee + Z-Wave over Ethernet) running alongside Z2M has zero conflict with OTBR — completely isolated
- FRITZBox 7590 does not need any special mDNS configuration for this setup — the Sync Thread credentials step in the Companion app resolves the discovery issue
- HAOS dark theme can hide configuration fields — if a field appears missing try switching to light theme temporarily
Hope this saves someone hours of troubleshooting! 