I also tried on Linux now, and this is the output of the GUI during attempted firmware upgrade:
fabian@gauss ~ $ Flirc
Can't load 'test.ini'
[DEVICE] Uploading
[D] lib/libflirc/bootloader/bl_3.3.c fl_ver_upload_fw(387): invalid image, incorrect sku
[D] lib/libflirc/bootloader/bl_3.3.c fl_ver_upload_fw(388): File Device
[D] lib/libflirc/bootloader/bl_3.3.c fl_ver_upload_fw(389): ---- ------
[D] lib/libflirc/bootloader/bl_3.3.c fl_ver_upload_fw(390): Flirc 2.0 [dori] Flirc 2.0 [dorir
[D] lib/libtransport/transport.c _dev_send_cmd(243): Command error: 128
[D] lib/libflirc/bootloader/bl_3.3.c bootloader_enter_app(197): Image CRC mismatched
[D] lib/libflirc/flirc_driver.c fl_upgrade_fw_ext(1087): upload firmware failed
[D] lib/libflirc/flirc_driver.c fl_major_version(391): something bad happened
[D] lib/libflirc/flirc_driver.c fl_minor_version(381): something bad happened
[D] lib/libflirc/flirc_driver.c fl_patch_version(401): something bad happened
[D] lib/libflirc/flirc_driver.c fl_major_version(391): something bad happened
[D] lib/libflirc/flirc_driver.c fl_minor_version(381): something bad happened
[D] lib/libflirc/flirc_driver.c fl_patch_version(401): something bad happened
It appears, that somehow the Device responds with "Flirc 2.0 [dorir" instead of the expected "Flirc 2.0 [dori]". Strange...
fabian@gauss ~ $ flirc_util sku
product sku: Flirc 2.0 [dorir