HAOS 18.x: Kernel forces IPv6 forwarding = 0 → OTBR broken → Matter-over-Thread commissioning fails

Intel NUC (Haswell generation)

Internal storage: Kingston SM2280S3G2/120G SSD

Network: Gigabit Ethernet (Wi‑Fi disabled)

Sonoff ZBDongle‑E (EFR32MG21)

    Running in RCP mode for OTBR

    Connected directly to USB port (no hub)

Sonoff ZBDongle‑P

    Used as Zigbee coordinator for Zigbee2MQTT

    Connected directly to USB port

No other USB devices attached

OTBR add-on using the Sonoff Dongle‑E

Matter server enabled

IKEA DIRIGERA also present on the network (used as secondary Thread BR)

Install HAOS 18.x on bare‑metal x86‑64

    Use an Intel NUC (Haswell) with a Kingston SSD as system disk.

    No hypervisor, direct HAOS install.

Attach Thread and Zigbee radios

    Plug in Sonoff ZBDongle‑E (EFR32MG21) for OTBR (RCP mode).

    Plug in Sonoff ZBDongle‑P for Zigbee2MQTT.

    Both directly on USB ports (no hub).

Enable OTBR and Matter in Home Assistant

    Install and start the OTBR add-on using the ZBDongle‑E.

    Enable Matter server in Home Assistant.

Check IPv6 forwarding on HAOS 18.x

    Open the HAOS terminal and run:
    bash

    cat /proc/sys/net/ipv6/conf/all/forwarding

    Observe that the value is always 0.

Attempt Matter-over-Thread commissioning

    Try to commission a Matter-over-Thread device (e.g. IKEA GRILLPLATS).

    Commissioning fails; OTBR logs show NoAck, SRP DNS drops, and Secure Pairing Failed.

Rollback HAOS to 17.3

    Use the Supervisor / CLI to roll back to HAOS 17.3.

    After rollback, check boot slots via:
    bash

    ha os info

    Slot B is booted, version 17.3, slot A is inactive, version 18.3.

Verify kernel and forwarding after rollback

    Check kernel version:
    bash

    uname -a

    → still shows a 6.8.x-haos kernel (from 18.x).

    Check IPv6 forwarding again:
    bash

    cat /proc/sys/net/ipv6/conf/all/forwarding

    → still 0.

Attempt to downgrade inactive slot A

    Try to update slot A to 17.3 via:
    bash

    ha os boot-slot A
    ha os update --version 17.3

    HAOS blocks the operation with messages like:
    OSManager.update blocked from execution, system is not running – startup  
    and refuses to downgrade the inactive slot.

Result

    System continues to boot with the 18.x kernel even when the active slot is 17.3.

    IPv6 forwarding remains 0.

    OTBR and Matter-over-Thread commissioning remain broken.

Supervisor logs do not show any OSManager, slot, downgrade or IPv6-related errors.

Host logs unavailable.

Home Assistant OS 18.x no longer exposes systemd/journalctl to SSH add-ons.
The Advanced SSH & Web Terminal add-on runs in a restricted host shell without journalctl.

I will provide host logs after accessing the physical console of the NUC.