update from V1.1.1 to 1.3.1 on iot2050 advanced fs:01

I would like to update from V1.1.1 to 1.3.1 on iot2050 advanced fs:01.

Using V1.1.1 I have performed the firmware update  to (Version 1.3, 04/2023) as described in the guide. I have cleared the eMMC beforehand  and boot order chosen was as suggested with mmc0 first. But with both V1.1.1 or V1.3.1 on the SD card  I now get a red stat led on boot attempts and device is not accessible on the network.

So it seems I have already bricked a few iot2050 advanced fs:01 this way with the firmware update...

I should mention that using the Displayport cable to DVI on a monitor never worked on any of those devices unfortunately so I don't really see whats going on. (but same cable does work on an ET200sp OpenController)

Any suggestions what could be useful next steps?

Document "IOT2050 Setting Up with Example Image Version 1.2.1, 03/2023" does mention to connect via UART on X14 but does not give specifics on the pinout of X14. Anyone can help? What would be ways to diagnose whats going on using the UART?

Another question is what Debian version V1.3.1 is based on? Would that be Debian "Bookworm"? (Just trying to understand if rescuing the bricked IOT2050s would be worth it at all.

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Split from Firmware Update to use Example Image as of V1.2.1 and Industrial OS as of V3.2.2.