Hi. I had the same problem. Device not detected. You just need to remove the sim card. Boot into Download mode. I used Heimdall 1.4.1 on Linux. Device will then be detected.
Plus - i have found that i need to use an older data cable. I’m guessing USB2.0. I can’t explain this, it just doesn’t detect the device for me without an old cable and sim removed. Tried both Heimdall 1.4.1 & 1.4.2.
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