Just added the OpenThread Border Router add-on to the development add-on repository
It is built directly from the upstream OpenThread sources, specifically the OpenThread Border Router for POSIX platforms. So far I joined nRF52840-Dongle based CLI devices (ot-cli-ftd, basically Thread devices with a CLI for testing). I’ve tested it using Nordic Semiconductor with the USB nRF52840-Dongle as well as with Silicon Labs EFR32 MGM210P flashed with OpenThread RCP firmware (the radio on Yellow).
The work is based on my previous SiliconLabs Zigbee/OpenThread Multiprotocol Add-on. This add-on uses the vanilla/upstream OTBR. It supports regular OpenThread RCP protocol radios (it does not support the SiliconLabs specific CPCd as the above add-on does). Ideally the SiLabs Multiprotocol add-on should be stripped of its forked version of OTBR and reuse the upstream OTBR version, however, for that to be possible upstream OTBR would need to gain CPCd support.