Hi @t1nux ,
I am glad that in the latest version of the HA Companion APP on the Android system, has an integrated ability to add the device of Matter over Thread.
The S200 TBR and mobile phone need to be connected to the same main router as follows.
In the testing, although I could ping the OMR address of the S200 and the Matter device from the mobile phone, the HA Companion App could not add the Matter device in the end. I tried using a Raspberry Pi as a TBR and had the same problem. It seems that HA does not fully support the third-party Thread Border Router.