No TouchBack support on Surface Hub 3 85" with USB-C/TB4 cables and up-to-date drivers

Hello,

Important linked thread which ended-up concluding Touchback is not supported for Surface Hub 3 85" here. Cross-posting from here.

I've been trying to setup touchback/inkback support several times on a Surface Hub 3 85". I'm doing everything as told in the Connect Devices guide or this other useful guide (for the Hub 2S, but I ordered a Hub 3 which has just a more beefy compute cartridge) from a Windows 11 Pro laptop 23H2 build

I've updated the drivers on the host PC, installed Surface Hub Replacement PC Drivers, that is connected to the Hub via the USB-C port below, on the compute cartridge, with either a USB-C standard cable or thunderbolt TB 4 cable. Display passes through correctly, device appears in device manager (HID compliant touchscreen etc), drivers were installed automatically and also updated with Snappy Driver Installer Origin SDIO. There is no button switch like on the older 1 hub to alternate between Guest/replacement mode and standard hub.

I also tried the configuration where the display/AV was passing through HDMI/Display-port and additional usb-c cable connected for devices, but this is not supported either - was again detected as a display, which I de-activated to try to give priority to device passthrough. I've read several comments on internet like this one or this one which have faced the same problem, but no official statement from microsoft stating that Touchback is not supported on the Surface Hub 3 85". Would love some insights.

Best regards,

Jonathan