Unfortunately it seems that Ikea is now enabling lock bits on their Zigbee devices. I also had to build a custom version of openocd to talk to this efm32s2 MCU https://github.com/knieriem/openocd-efm32-series2
And after sending a efm32s3_dci_device_erase command, I can debug the chip. So thanks for the $5 dev board with boost converter, Ikea, even if we have to start from zero for the firmware.
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